Martensitic heat-resisting steel excellent in HAZ-softening resistance and process for producing the same

ABSTRACT

A martensitic heat-resisting steel comprises, in terms of % by mass, 0.01 to 0.30% of C, 0.02 of 0.80% of Si, 0.20 to 1.00% of Mn, 5.00 to 18.00% of Cr, 0.005 to 1.00% of Mo, 0.20 to 3.50% of W, 0.02 to 1.00% of V, 0.01 to 0.50% of Nb, 0.01 to 0.25% of N, and at least one element selected from the group consisting of Ti, Zr, Ta and Hf in an amount of 0.005 to 2.0% for each of the elements, the volume of (Ti %+Zr %+Ta %+Hf %) in the metal component M of M 23  C 6  type carbides therein being from 5 to 65%. The heat-resisting steel is produced by a process comprising the steps of 
     adding Ti, Zr, Ta and Hf to a molten steel having chemical components as mentioned above, during the period from 10 minutes before completion of refining to completion of refining, casting said molten steel, working the resulting casting, solution treating said worked product, subjecting said worked product to temporary cooling stop at a temperature from 950° to 1,000° C. in the course of cooling said hot worked product, and holding said worked product at the temperature for 5 to 60 minutes. The heat-resisting steel is excellent in HAZ-softening resistance, and exhibits a high creep strength at high temperature of at least 550° C.

FIELD OF THE INVENTION

The present invention relates to a martensitic heat-resisting steel, and more in detail, to a martensitic heat-resisting steel excellent in HAZ-softening resistance and used in a high temperature and high pressure environment.

BACKGROUND OF THE INVENTION

Boilers of thermal power plants have been operated under conditions of markedly high temperature and high pressure in recent years. Part of them are planned to be operated at 566° C. and 316 bar. It is estimated that some of them will operate at 649° C. and 352 bar in the future. Accordingly, materials for such boilers will be used under extremely harsh conditions.

When the operation temperature exceeds 550° C., materials used in the boilers will be changed, for example, from ferritic 21/4% Cr-1% Mo steel to an austenitic steel of high grade such as 18-8 stainless steel in view of oxidation resistance and high temperature strength. Thus, materials of very high grade and high cost are currently used.

Steel materials having an intermediate grade between 21/4% Cr-1% Mo steel and austenitic stainless steel have been searched for in the past several decades. Boiler tube steels containing an intermediate amount of Cr such as 9% Cr steel or 12% Cr steel have been developed on the basis of the demands described above. Some of the steels have attained a high temperature strength and a creep strength comparable to austenitic steels by precipitation strengthening or solid solution strengthening effected by adding a variety of alloying elements as base material components.

The creep strength of heat-resisting steels is governed by solid solution strengthening when the steels have been aged for a short period of time and by precipitation strengthening when they have been aged over a long period of time. This is because solid solution strengthening elements dissolved in the steels are precipitated at first as stable carbides such as M₂₃ C₆ by aging in many cases. However, when the steels are aged for a still longer period of time, the precipitates are coalescence coarsened, and as a result the creep strength is lowered. Many studies have, therefore, been performed on maintaining the solid solution strengthening elements in a solution state in the steels over a long period of time without precipitation in order to maintain the high creep strength of the heat-resisting steels.

For example, Japanese Patent Unexamined Publication (Kokai) Nos. 63-89644, 61-231139 and 62-297435 disclose ferritic heat-resisting steels which can achieve a creep strength far higher than a conventional Mo-added type ferritic heat-resisting steel by the use of W as a solid solution strengthening element. Many of these steels have a tempered martensite single phase as their structure, and are expected to become the next generation of materials for use in high temperature and high pressure environments due to their advantage as ferritic steels excellent in steam oxidation resistance and due to their high strength properties.

On the other hand, ferritic heat-resisting materials utilize the high strength of a martensite structure containing a large amount of dislocations or its tempered structure formed by the supercooling phenomenon of phase transformation from an austenite single phase region to (ferrite+carbide precipitate) the phase to be produced as a result of cooling during heat treatment. Accordingly, when the structure is subjected to a heat cycle of being reheated to the austenite single region, for example, when the structure is subjected to weld heat affection, the dislocations of high density are relieved again, and the strength is sometimes locally decreased in the weld HAZ (heat-affected zone).

Particularly among those portions which are reheated to a temperature of at least a ferrite-austenite transformation point, portions which has been heated to a temperature near the transformation point, for example, about from 900° to 1,000° C. in the case of 9% Cr steel, and recooled in a short period of time are subjected to martensite transformation while austenite grains do not grow sufficiently to become a fine grain structure. In addition, M₂₃ C₆ type carbides which are a principal factor in improving the materials strength by precipitation strengthening do not redissolve, and mechanisms for inducing a decrease in the high temperature strength such as alteration of the constituent components of the carbides, or carbide coarsening, may compositely act on the portion to locally become a softened zone. The softening zone-forming phenomenon is termed "HAZ-softening" for convenience.

DISCLOSURE OF THE INVENTION

The present inventors have carried out detailed studies on the softening zone, and found that the decrease in strength is caused mainly by a change of the constituent elements in M₂₃ C₆ type carbides. As the result of further investigation, they discovered that when high strength martensitic heat-resisting steel is being subjected to the weld heat affection, Mo or W particularly essential to solid solution strengthening thereof is dissolved in the constituent element M of M₂₃ C₆ in a large amount and precipitates at grain boundaries of the fine grain structure, and that as a result, a Mo- or W-depleted zone is formed near the austenite grain boundaries, resulting in a local decrease in the creep strength.

Accordingly, the decrease in the creep strength caused by weld heat affection is critically disadvantageous to heat-resisting materials. It is obvious that the prior art aiming at optimization of heat treatment and welding cannot solve the problems. In addition, it is evident that a countermeasure of completely austenitizing a welded portion again which had been recognized as the sole solution cannot be practiced when the process of construction and execution of works in power plant is taken into consideration. Accordingly, it is clear that manifestation of the "HAZ-softening" phenomenon is inevitable in a conventional heat-resisting martensitic or ferritic steel.

An object of the present invention is to overcome the disadvantage of the conventional steel, namely to avoid the formation of a local softening zone in a weld HAZ caused by alteration and coarsening of M₂₃ C₆ type carbides.

A further object of the present invention is to prevent Mo or W from being dissolved in M₂₃ C₆ in a large amount while the steel material is being subjected to weld heat affection.

To achieve the objects as mentioned above in the present invention, the composition and the precipitation size of M₂₃ C₆ type carbides in a weld HAZ are controlled.

As the result of intensively investigating the "HAZ-softening" phenomenon to achieve the objects as mentioned above, the present inventors have discovered that Ti, Zr, Ta and Hf each have an extremely strong affinity with C in the component system of the steel according to the present invention, that carbides of these elements become precipitation nuclei of M₂₃ C₆ carbides to be precipitated in the tempered martensite structure of the steel according to the present invention, and these elements dissolve in solid solution state at the same time in the metal component M in the carbides, that when the solid solution amount in the metal component M is within a specific range, the creep rupture strength of the weld HAZ falls down to only an extremely small value within the deviation of the creep rupture strength of the base material compared with the rupture strength thereof, and that as a result, the weld HAZ does not exhibit the "HAZ-softening" phenomenon any more.

The following process has been developed to realize the discovery.

First, since the precipitates of Ti, Zr, Ta and Hf are each required to become fine and appropriate, that is, since all of the precipitates must become carbides and carbonitrides, these elements are each added to the molten steel in a state of a low oxygen concentration immediately before completion of refining. Second, since these precipitates of Ti, etc. are required to become precipitation nuclei of M₂₃ C₆ to be precipitated within the tempered martensite structure and to be dissolved in solid solution state in the resultant carbides in suitable amounts, the steel slab is processed as follows: the steel slab having been subjected to a solid solution heat treatment is subjected to cooling stop at a temperature of 950° to 1,000° C. in the course of cooling; and the steel slab is held at the temperature for a predetermined period of time to sufficiently precipitate fine carbides of Ti, etc.

As described above, when a steel material having a martensite structure in which fine carbides of Ti, etc. are precipitated is tempered, M₂₃ C₆ type carbides are precipitated while the carbides of Ti, etc. are utilized as the precipitation nuclei. M₂₃ C₆ carbides and the fine carbides of Ti, Zr, Ta and Hf are mutually dissolved in each other, and finally M₂₃ C₆ type carbides in which Ti, Zr, Ta and Hf are solid solubled in the prescribed range in the metal component M, are formed in the tempered martensite structure. As a result, the creep rupture strength of the weld HAZ is significantly improved.

That is, the present invention provides a martensitic heat-resisting steel which comprises, in terms of % by mass, 0.01 to 0.30% of C, 0.02 to 0.80% of Si, 0.20 to 1.00% of Mn, 5.00 to 18.00% of Cr, 0.005 to 1.00% of Mo, 0.20 to 3.50% of W, 0.02 to 1.00% of V, 0.01 to 0.50% of Nb, 0.01 to 0.25% of N, up to 0.030% of P, up to 0.010% of S, up to 0.020% of O, at least one element selected from the group consisting of Ti, Zr, Ta and Hf in an amount of 0.005 to 2.0% for each of the elements, if necessary at least one element selected from the group consisting of Co, Ni and Cr in an amount of 0.2 to 5.0% for each of Co and Ni and 0.2 to 2.0% for Cu, and the balance Fe and unavoidable impurities, and which has in the tempered martensite structure precipitated M₂₃ C₆ type carbides, the value of (Ti %+Zr %+Ta %+Hf %) in the metal component M thereof being from 5 to 65%. The present invention provides a process for producing said heat-resisting steel comprising the steps of adding at least one element selected from the group consisting of Ti, Zr, Ta and Hf to a molten steel during the period from 10 minutes before completion of refining to completion thereof, subjecting the steel to temporary cooling stop at a temperature of 950° to 1,000° C. in the course of cooling the steel after solution heat treatment, holding the steel at that temperature for 5 to 60 minutes, and tempering it.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a butt groove shape of a welded joint.

FIG. 2 is a view showing a procedure for sampling test pieces for analyzing precipitates in a weld HAZ.

FIG. 3 is a diagram showing the relationship between the addition time of Ti, Zr, Ta and Hf, and the form and the average particle size of precipitates of Ti, Zr, Ta and Hf in the steel.

FIG. 4 shows graphs each showing the relationship between a temporary cooling stop temperature after solution treatment and a holding time thereat, and the particle size of the precipitated carbides.

FIG. 5 is a diagram showing the relationship between a temporary cooling stop temperature after solution treatment, and the form and the structure of the precipitates in a weld HAZ.

FIG. 6 is a graph showing the relationship between a difference (D-CRS) between the creep rupture strength at 600° C. for 100,000 hours estimated by linear extrapolation of a base steel and that of a weld HAZ, and the value of M % (Ti %+Zr %+Ta %+Hf %) in M of M₂₃ C₆ type carbides in the weld HAZ.

FIG. 7 is a graph showing the relationship between the creep rupture strength at 600° C. for 100,000 hours estimated by linear extrapolation of a base steel and the value of Ti %+Zr %+Ta %+Hf % in the base steel.

FIG. 8 is a graph showing the relationship between the value of M % (Ti %+Zr %+Ta %+Hf %) in M of M₂₃ C₆ type carbides in the weld HAZ and the toughness thereof.

FIG. 9(a) and FIG. 9(b) are views showing a procedure for sampling a creep rupture strength test piece from a steel tube and a procedure therefor from a plate or sheet, respectively.

FIG. 10(a) and FIG. 10(b) are views showing a procedure for sampling a creep rupture test piece from a weld zone of a steel tube and a procedure therefor from a weld zone of a plate or sheet, respectively.

FIG. 11(a) and FIG. 11(b) are views showing a procedure for sampling a Charpy impact test piece from a weld zone of a steel tube and a procedure therefor from a weld zone of a plate or sheet, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be explained.

First, the reasons for restricting the contents of components in the molten steel in the present invention as mentioned above are described below. A content expressed in terms of % signifies a content in terms of % by mass.

Though C is necessary for maintaining the strength of the steel, C in a content of less than 0.01% is insufficient for ensuring the strength of the steel. When the content of C exceeds 0.30%, the weld HAZ is markedly hardened, and as a result cold cracking is formed at the time of welding. Accordingly, the content range of C is defined to be from 0.01 to 0.30%.

Si is important in ensuring the oxidation resistance of the steel, and it is also a necessary element as a deoxidizing agent. Si in a content of less than 0.02% is insufficient, and Si in a content exceeding 0.80% lowers the creep strength of the steel. Accordingly, the content range of Si is defined to be from 0.02 to 0.80%.

Mn is a component necessary not only for deoxidization but also for maintaining the strength of the steel. Addition of Mn in a content of at least 0.20% is necessary for obtaining a sufficient effect. Mn in a content exceeding 1.00% may sometimes lower the creep strength of the steel. Accordingly, the content range of Mn is defined to be from 0.20 to 1.00%.

Cr is an element essential to the oxidation resistance of the steel. Cr combines with C at the same time in forms of Cr₂₃ C₆ ·Cr₇ C₃, etc. to form fine precipitates in the base steel matrix, and thus contributes to an increase in the creep strength of the steel. From the standpoint of oxidation resistance, the lower limit of the Cr content is defined to be 5.0%. The upper limit thereof is defined to be 18.0% from the standpoint of ensuring a high temperature strength of the steel and in view of the limit for achieving a martensite single phase.

W is an element significantly enhancing the creep strength of the steel through solution hardening. W particularly increases the long term creep strength at high temperatures of at least 550° C. When K is added in a content exceeding 3.5%, it precipitates mainly at grain boundaries as intermetallic compounds in a large amount. As a result, the toughness and the creep strength of the base steel are markedly lowered. The upper limit of the W content is, therefore, defined to be 3.5%. Moreover, W in a content of less than 0.20% is insufficient for achieving the effect of solid solution strengthening. Accordingly, the lower limit of the W content is defined to be 0.20%.

Mo also enhances the high temperature strength of the steel through solid solution strengthening. Mo in a content of less than 0.005% is insufficient for achieving the effect. Since Mo₂ C type carbide is precipitated in a large amount or Mo₂ Fe type intermetallic compound is precipitated when the content of Mo exceeds 1.00%, simultaneous addition of Mo and W may considerably lower the toughness of the base steel. Accordingly, the upper limit of the Mo content is defined to be 1.00%.

V is an element which significantly enhances the high temperature creep rupture strength of the steel when it is precipitated as precipitates or when it is dissolved in the matrix in the same manner as W. In the present invention, V in a content of less than 0.02% is insufficient for precipitation strengthening the steel with V precipitates, and on the other hand V in a content exceeding 1.00% forms clusters of V type carbides or carbonitrides which lower the toughness of the steel. Accordingly, the V content is defined to be from 0.02 to 1.00%.

Nb precipitates as NX type carbides or carbonitrides to increase the high temperature strength of the steel and contribute to solid solution strengthening. When the Nb content is less than 0.01%, the addition effects are not noticeable. When the Nb content exceeds 0.50%, coarse precipitates are formed to lower the toughness. Accordingly, the addition content range of Nb is defined to be from 0.01 to 0.50%.

N is dissolved in the matrix or precipitates as nitrides and carbonitrides. N contributes to solution hardening and precipitation hardening of the steel principally in the forms of VN, NbN or their carbonitrides. N in an addition content of less than 0.01% exhibits almost no contribution to strengthening of the steel. Moreover, the upper limit of the addition content thereof is defined to be 0.25% while the upper limit of the addition content thereof in molten steel in accordance with the Cr addition content of up to the maximum value of 18% is taken into consideration.

The addition of Ti, Zr, Ta and Hf constitutes the foundation of the present invention. The addition of these elements and the process according to the present invention realizes prevention of the "HAZ-softening" in the steel of the invention. Ti, Zr, Ta and Hf have an extremely strong affinity with C in the component system of the steel of the invention, and dissolve in M of M₂₃ C₆ as constituent elements to raise the decomposition temperature thereof. Accordingly, these elements are effective in preventing M₂₃ C₆ from coarsening in the "HAZ-softening" zone. In addition, these elements prevent W and Mo from dissolving in M₂₃ C₆, and, therefore, a zone depleted in W and Mo is not formed around the precipitates. These elements may be added singly or compositely in a mixture of at least two of them. These elements each in a content of at least 0.005% already show the effects. Since any one of these elements in a content of at least 2.0% forms coarse MX type carbides and deteriorates the toughness of the steel, the addition content range of each of them is defined to be from 0.005 to 2.0%.

P, S and O are mixed into the steel of the invention as impurities. However, in view of displaying the effect of the invention, P and S lower the strength, and O precipitates as an oxide and lowers the toughness of the steel. Accordingly, the upper limits of P, S and O are defined to be 0.03, 0.01 and 0.02%, respectively.

Though the fundamental components of the steel of the present invention are as described above, the steel of the invention may optionally contain one or at least two elements selected from the group consisting of Ni, Co and Cu. The steel of the invention may contain from 0.1 to 5.0% of Ni, from 0.1 to 5.0% of Co and from 0.1 to 2.0% of Cu.

Ni, Co and Cu are all potent elements for stabilizing austenite structure. Particularly when large amounts of ferrite-stabilizing elements, namely Cr, W, Mo, Ti, Zr, Ta, Hf, Si, etc., are added, Ni, Co, Cu are necessary for obtaining complete martensite or its tempered structure, and these elements are useful. At the same time, Ni and Co are effective in improving the toughness and the strength of the steel, respectively, and Cu is effective in improving the strength and corrosion resistance thereof. A content of each of these elements of less than 0.1% is insufficient for achieving these effects. When Ni or Co are each added in a content exceeding 5.0% or when Cu is added in a content exceeding 2.0%, it is inevitable that coarse intermetallic compounds are precipitated in the case of adding Ni or Co, and that intermetallic compounds are formed in a film form along grain boundaries in the case of adding Cu.

These elements are, therefore, added in the content ranges as mentioned above. However, since the above-mentioned effects of adding these elements become significant when they are each added in a content of at least 0.2%, the lower limit of the addition content of each of these elements is desirably 0.2%.

To obtain appropriate effects of adding Ti, Zr, Ta and Hf, the value of (Ti %+Zr %+Ta %+Hf %) in the metal component M of M₂₃ C₆ type carbides existing in the weld HAZ is required to be from 5 to 65%. To satisfy the requirement through precipitation of these elements in the form of appropriate carbides in the steel, the steel production process is carried out as follows: Ti, Zr, Ta and Hf are added during the period from 10 minutes before completion of refining to completion of refining; cooling the steel subsequent to solution treatment which is usually performed by holding the steel at temperature of 900° to 1,350° C. for a period of 10 minutes to 24 hours is temporarily stopped at a temperature from 950° to 1,000° C., and the steel is held at the temperature for a period of 5 to 60 minutes to control the precipitated forms of the carbides. The precipitates thus obtained can be utilized as precipitation nuclei of M₂₃ C₆ mainly containing Cr to be precipitated subsequent tempering, which is usually carried out by holding the steel at a temperature of 300° to 850° C. for a period of 10 minutes to 24 hours. The effects of adding Ti, Zr, Ta and Hf can be appropriately manifested and the object of the invention can be achieved only by applying the process as mentioned above. The intended effects of the present invention cannot be achieved even if a steel is produced merely by a conventional process using materials having the adjusted chemical composition of the invention. That is, the value of (Ti %+Zr %+Ta %+Hf %) in the metal component M of M₂₃ C₆ type carbides existing in the weld HAZ cannot be controlled to be from 5 to 65%.

The production process and the composition range of carbides as mentioned above have been determined by experiments as described below.

A molten steel having a chemical composition as claimed in the claims of the present invention except for Ti, Zr, Ta and Hf was prepared by using a VIM (vacuum induction heating furnace) or EF (electric furnace), and selecting and using an AOD (argon-oxygen blowing decarbonization refining unit), a VOD (vacuum exhausting oxygen blowing decarbonization unit) or LF (molten steel ladle refining unit), and cast into a slab having a cross section of 210×1,600 mm by a continuous casting unit. The influence of the addition time of Ti, Zr, Ta and Hf on the composition and the shape of precipitates after casting was investigated by adding these elements at any of the following times: at the start of melting, during melting or 5 minutes before completion of melting in a VIM or EF; at the start of refining process or 10 minutes before completion thereof in an AOD, a VOD or LF. Each of the slabs thus cast was sectioned so that each piece thus obtained had a length of 2 to 5 m and plates each having a thickness of 25.4 mm were formed. The plates were then solution treated under the conditions of the maximum heating temperature of 1,100° C. and a holding time of 1 hour. In the course of cooling the plates, cooling was stopped at a temperature of 1,050°, 1,000°, 950°, 900°, 850° or 800° C., and the plates were held at the temperature for up to 24 hours in the furnace and air cooled. Precipitates in the plates were then subjected to residue-extraction analysis, and the precipitation forms of carbides in the plates were examined using a transmission electron microscope with a micro X-ray analysis apparatus.

Furthermore, each of the steel plates thus obtained was tempered at 780° C. for 1 hour, subjected to edge preparation for V-shaped butt welding with a groove angle of 45 degrees, and used for welding experiments. The experiments were carried out by using TIG arc welding under a selected heat input condition of 15,000 J/cm which is a general heat input for martensitic heat-resisting materials.

The welded joint samples thus obtained were subjected to post weld heat treatment at 740° C. for 6 hours, and thin film disc samples for transmission electron microscopic observation and block test pieces for extraction-residue analysis were sampled from the HAZ portions of the samples by procedures as shown in FIG. 2.

FIG. 3 shows the relationship between the addition time of Ti, Zr, Ta and Hf, and the form and the average particle size of precipitates of Ti, Zr, Ta and Hf in the steel. In order that the precipitates of Ti, Zr, Ta and Hf may become precipitation nuclei of M₂₃ C₆ and solid soluble in the constituent metal element M of M₂₃ C₆, these elements must exist as fine carbides (including carbonitrides) in advance in the molten metal. It is understood that to satisfy the requirement, these elements are required to be added to molten steel having a low oxygen concentration, that is, these elements must be added to molten steel during the period from 10 minutes before completion of refining in a VOD or LF to at the time of completion thereof. The average particle size of carbides at this time, namely carbides in steels produced by casting the molten steels or ingot-making thereof has been found to be approximately 0.15 μm by electron microscopic observation of the carbides.

The particle size of the precipitates should desirably be made as small as possible in view of the precipitation strengthening mechanism.

When the cast slab, etc. thus obtained is subjected to hot working, solution treatment, cooling (air cooling) to room temperature, working and tempering, carbides of Ti, etc. precipitated in the tempered worked product become fine. However, the amount of the carbides thus formed is only about half as much as that of carbides of Ti, etc. having been precipitated in the slab at the time of its production. In addition, the carbides are precipitated as MC type carbides other than M₂₃ C₆ type carbides. As a result, the "HAZ-softening" phenomenon takes place in the tempered worked product.

As a result of investigating the relationship between cooling conditions after solution treatment and precipitated carbides using cast slabs (having chemical components the contents of which are in the range as claimed in the claims of the present invention) produced by the process of EF-LF-CC, the present inventors have clarified that the cooling stop temperature subsequent to solution treatment and the holding time at the temperature have an extremely important relationship with the particle size of the precipitated carbides.

That is, it has been confirmed that the average particle size of carbides precipitated in the steels becomes smallest when the cooling stop temperature and the holding temperature are from 950° to 1,000° C. and that most of the carbides having been precipitated in the cast slabs are reprecipitated when the slabs are held for a holding time of 5 to 60 minutes.

Taking the research results as described above into consideration, the present inventors carried out the following experiments: cast slabs, etc. used in FIG. 3 were worked, solution treated, subjected to air cooling which was stopped at a variety of temperatures including 950° C. and 1,000° C., held at respective cooling stop temperatures for 30 minutes, and further air cooled to room temperature; the samples thus obtained were tempered at 780° C. for 1 hour; the samples were welded, and heat treated; and the relationship between the forms and compositions of the principal precipitates in the weld HAZ, and the cooling stop temperature was investigated. The results thus obtained are shown in FIG. 5. It is seen from FIG. 5 that the carbides which take the finest precipitation forms prior to tempering (carbides in the steels which have been subjected to cooling stop at a temperature of 950° C. or 1,000° C.) become precipitation nuclei of M₂₃ C₆, that the carbides and M₂₃ C₆ precipitated during tempering mutually dissolve in each other to finally form M₂₃ C₆ type carbides, and that Ti, Zr, Ta and Hf are dissolved in the constituent metal element M in a proportion of 5 to 65% in total.

Furthermore, it has been found that the weld HAZ as mentioned above has a very high creep rupture strength at high temperature.

FIG. 6 shows the relationship between a difference (D-CRS (MPa)) between the creep rupture strength of the base steels at 600° C. for 100,000 hours and that of the weld HAZ, and the value of M % (Ti %+Zr %+Ta %+Hf %) in M₂₃ C₆ type carbides in the weld HAZ. When M % is from 5 to 65, the creep rupture strength of the weld HAZ decreases by only up to 7 MPa compared with that of the base steels. Since the difference is within the deviation of the creep rupture strength data of the base steels (10 MPa), it is understood that the weld HAZ no longer exhibits HAZ-softening. It can be concluded that the experimental results are brought about for the following reasons: M₂₃ C₆ type carbides containing from 5 to 65% of Ti, Zr, Ta and Hf in the constituent element M have a high decomposition temperature compared with ordinary M₂₃ C₆ type carbides containing mainly Cr in M, and are not subject to be coalescence coarsening even after weld heat affection; moreover, W and Mo are extremely difficult to dissolve in place of or in addition to Ti, Zr, Ta and Hf due to their chemical affinities and phase diagrams.

In addition, each of the elements Ti, Zr, Ta and Hf influences the creep strength of the base steels.

FIG. 7 shows the relationship between the creep rupture strength of the base steels at 600° C. for 100,000 hours and the value of Ti %+Zr %+Ta %+Hf % in the base steels. It is evident from FIG. 7 that excessive addition of Ti, Zr, Ta and Hf causes precipitate coarsening, and that as a result the creep rupture strength of the base steels themselves decreases. When the total amount of Ti %+Zr %+Ta %+Hf % in the base steels is up to 8%, the creep rupture strength thereof becomes at least the evaluation standard value of 130 MPa and causes no problem. When the upper limit of the total amount of Ti, etc. is 8%, the content of each of the elements Ti, Zr, Ta and Hf does not exceed 2%, and is within the content range as claimed in the present invention.

Next, the toughness of the weld HAZ of the steel according to the present invention will be explained. FIG. 8 shows the relationship between the value of Ti %+Zr %+Ta %+Hf %, namely M % in M₂₃ C₆ in the weld HAZ and the toughness of the weld HAZ. It is understood from FIG. 8 that when M % exceeds 65%, the precipitates are coarsened and the toughness of the weld HAZ decreases, and that the toughness falls below the evaluation standard value of 50 J.

In addition, in the toughness test, a 2 mmV-notched Charpy impact test piece 11 in accordance with JIS No.4 was cut out of a portion containing a weld zone and located in the direction normal to the weld line as shown in FIG. 11(a) and FIG. 11(b). The notch was formed at a weld bond 9, which was represented by the hardest portion and shown. The evaluation standard value was defined to be 50 J at 0° C. while the construction conditions of heat-resisting materials were taken into consideration. The reference numeral 10 designates a weld HAZ.

As described above, the steel of the invention having a value of 5 to 65% as M % is also excellent in toughness.

The process of the present invention has been determined as claimed in the claims on the basis of the results as mentioned above. When a steel having a chemical composition according to the present invention is produced without applying the process of the present invention, it is impossible to obtain in the weld HAZ M₂₃ C₆ carbides having the same composition as mentioned in the present invention.

There is no limitation on the method for melting the steel of the invention. The process can be determined in a satisfactory way taking into consideration converters, induction heating furnaces, arc melting furnaces, electric furnaces, etc., and chemical components and the cost of the steel. The unit used in the refining step is required to be equipped with a hopper which can add Ti, Zr, Ta and Hf and which is capable of controlling the oxygen concentration in the molten steel at a sufficiently low one so that at least 90% of these added elements can be precipitated as carbides. Accordingly, an LF equipped with an Ar-blowing unit, an arc heating unit or plasma heating unit, or a vacuum degassing unit is advantageously used. The use of them will enhance the effects of the invention.

Furthermore, in the subsequent rolling step or tube milling step in the case of producing a steel tube, solution treatment is essential for the purpose of uniformly redissolving the precipitates. There is required an installation capable of stopping the cooling of the steel at a given temperature in the course of cooling after solution treatment, and holding at that temperature, and a furnace which can heat the steel up to 1,350° C. is required. There can be applied production steps other than those mentioned above, concretely, all production steps recognized as necessary or useful for producing a steel or a steel product by the present invention, for example, forging, rolling, heat treatment, tubing, welding, sectioning, inspection, and the like. Their application by no means impairs the effects of the present invention.

Particularly in the production of steel tubes, the following production processes of steel tubes can be applied to the present invention under the condition that the processes comprise the production steps of the present invention without fail: a process for producing a seamless pipe or tube comprising the steps of working a steel to form a round or square billet, and hot extruding or seamless rolling the billet in various ways; a process for producing an electric welded tube comprising the steps of hot rolling and cold rolling a steel sheet, and resistance welding the rolled sheet; and a process for producing a welded steel tube comprising carrying out TIG arc welding, MIG welding, SAW, LASER welding and EB welding singly or in combination. Furthermore, there can be additionally practiced after carrying out each of the processes as mentioned above any of hot or warm SR (squeeze rolling), sizing rolling, and a variety of levelling steps. The applicable size of the steel of the invention can thus be expanded.

The steel of the present invention may further be provided in the form of a plate or sheet. The plate or sheet having been subjected to necessary heat treatment may be used as a heat-resisting material with various shapes, and exerts no adverse effects in the present invention.

Still furthermore, there may be applied to the process of the present invention powder metallurgy processes such as HIP (hot isostatic press sintering unit), CIP (cold isostatic pressing unit) and sintering. Products having a variety of shapes can be obtained by subjecting the resultant compacted products to indispensable heat treatment.

The steel tubes, steel plates and heat-resisting steel materials of various shapes thus obtained may be subjected to respective heat treatments depending on the object and application. These heat treatments are important to obtain sufficient effects of the present invention.

Usually, the products of the invention are obtained through the steps of normalizing (solution treatment) and tempering. The products may further be retempered and/or normalized, and the step is useful. In addition, cooling stop at a temperature of the steel and holding it at the temperature after solution treatment are essential to the process of the invention.

When the steel of the invention has a relatively high content of nitrogen or carbon, when the steel contains austenite-stabilizing elements such as Co, Ni and Cu in a large amount or when the steel has a low Cr equivalent, the so-called sub-zero treatment wherein the steel is cooled to up to 0° C. may be applied thereto to avoid retained austenite phase formation. The treatment is effective in sufficiently manifesting the mechanical properties of the steel of the invention.

Each of the steps mentioned above may also be applied at least twice so long as the repetition of the steps is necessary for sufficiently manifesting the material properties, and the repetition exerts no adverse effects in the present invention.

The steps as mentioned above may suitably be selected and applied to the process for producing the steel of the present invention.

EXAMPLES

A molten steel having components except for Ti, Zr, Ta and Hf as shown in some of Table 1-1 to Table 25-3 was prepared in an amount of 300 ton, 120 ton or 60 ton by the blast furnace pig iron-converter blowing process, using a VIM or EF, and refined in an LF unit having an arc reheating unit and capable of blowing Ar. At least one of the elements Ti, Zr, Ta and Hf was added to the molten steel in amounts as shown in the table 10 minutes before completion of refining, and the molten steel was continuously cast to obtain a slab. The slab thus obtained was hot rolled to give a plate 50 mm thick and a sheet 12 mm thick, or the slab was worked to give a round billet which was hot extruded to give a tube having an outer diameter of 74 mm and a thickness of 10 mm or which was seamless rolled to give a pipe having an outer diameter of 380 mm and a thickness of 50 mm. The sheet was formed, and electric welded to give an electric welded steel tube having an outer diameter of 280 mm and a thickness of 12 mm.

All the plates, sheets and tubes thus obtained were solution treated at 1,100° C. for 1 hour, subjected to a temporary cooling stop at a temperature of 950° to 1,000° C. and held at that temperature for 5 to 60 minutes in the furnace, air cooled, and tempered at 780° C. for 1 hour.

The plates and sheets thus obtained were subjected to edge preparation exactly in the same manner as shown in FIG. 1. A groove which was the same as in FIG. 1 was formed in each of the tubes thus obtained at the edge in the circumferential direction. The worked plates and sheets were welded and the worked tubes were subjected to circular joint welding, by TIG arc welding or SAW welding. All the welded portions were locally subjected to softening annealing (PWHT) by heating them at 740° C. for 6 hours.

The creep characteristics of the base steels were obtained as follows: a creep test piece 5 having a diameter of 6 mm was cut out of a portion other than a weld zone and a weld HAZ in a steel tube 1 in the direction parallel to the tube axis direction 2 as shown in FIG. 9(a), or a creep test piece 5 of the same size was cut out of the same portion as mentioned above in a plate 3 in the direction parallel to the rolling direction 4 as shown in FIG. 9(b); a creep rupture strength was measured at 600° C. on the test piece, and the data thus obtained were linearly extrapolated to obtain a creep rupture strength for 100,000 hours. The creep characteristics of a weld zone was obtained as follows: a creep rupture test piece 8 having a diameter of 6 mm was cut out of each of the welded tubes or plates in a direction 7 normal to a weld line 6 as shown in FIG. 10(a) or FIG. 10(b); the results of measuring creep rupture strength at 600° C. were linearly extrapolated to 100,000 hours. The creep characteristics thus obtained were compared with those of the base steels and evaluated. For convenience of description in the present invention, a "creep rupture strength" (HAZCRS (MPa)) signifies a creep rupture strength at 600° C. for 100,000 hours estimated by linear extrapolation. A difference between the creep rupture strength of a base steel and that of a weld HAZ (D-CRS (MPa)) was used as an index of the "HAZ-softening" resistance of a weld zone. Although the value of D-CRS is somewhat influenced by the method of sampling a creep rupture test piece in the rolling direction of a sample, it has been empirically found by a preliminary experiment that the influence is within 5 MPa. Accordingly, a D-CRS value of up to 10 MPa signifies that the HAZ-softening resistance of the steel material is extremely good.

Test pieces for precipitates of a HAZ portion were sampled by the procedure as shown in FIG. 2, and subjected to extraction-residue analysis by acid dissolution to identify M₂₃ C₆, followed by determining the composition in M by a scanning type micro X-ray analysis apparatus. Ti %+Zr %+Ta %+Hf % thus obtained were represented by M %, and the precipitates were evaluated. The standard reference based on the experimental results is defined to be from 5 to 65%.

The values of D-CRS, HAZCRS and M % were shown in Table 1-3, Table 2-3 to Table 25-3 in the form of numerical data together with chemical components.

It is evident from the tables that the steels of the present invention No. 1 to No. 381 exhibited the maximum value of D-CRS of 7 MPa, the maximum value of HAZCRS of 180 MPa and the minimum value of HAZCRS of 130 MPa. Accordingly, the HAZ-softening resistance of the steels of the invention was extremely good.

For comparison, steels which did not correspond to any of the claims of the present invention were evaluated in the same manner. The chemical components and the values of D-CRS, HAZCRS and M % among the evaluation results are shown in Table 26-1 to Table 26-2.

Experimental results about comparative steels in Table 26-1 to Table 26-2 are as described below. Though No. 721 steel and No. 722 steel had the same chemical components as the steel of the invention, Ti and Zr were added at the time of melting. As a result, the value of M % became up to 5%, and the HAZ-softening resistance deteriorated. In No. 723 steel and No. 724 steel, Ti, Zr, Ta and Hf were not sufficiently added. As a result, M % became low, and the HAZ-softening resistance deteriorated. No. 725 steel, No. 726 steel, No. 727 steel and No. 728 steel were instances wherein a number of coarse MX type carbides were precipitated, composition control of M₂₃ C₆ in the weld HAZ could not be achieved, and as a result the HAZ-softening resistance deteriorated, due to excessive addition of Ti in the case of No. 725 steel, excessive addition of Zr in the case of No. 726 steel, excessive addition of Ta in the case of No. 727 steel and excessive addition of Hf in the case of No. 728 steel. Since a temporary cooling stop was not practiced after solution treatment in the production of No. 729 steel, composition control of M₂₃ C₆ therein could not be achieved, and the HAZ-softening resistance deteriorated. In the production of No. 730 steel, since the holding time was 240 minutes which was overly long after solution treatment and the temporary cooling stop, the precipitates therein were coarsened, and composition control of M₂₃ C₆ could not be achieved. As a result, the HAZ-softening resistance deteriorated.

                  TABLE 1-1                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         1    0.26   0.24   0.46 16.73                                                                               0.753                                                                               1.88 0.69 0.33 0.17                          2    0.24   0.63   0.68 16.40                                                                               0.126                                                                               0.92 0.44 0.44 0.03                          3    0.05   0.30   0.69 15.19                                                                               0.120                                                                               2.65 0.68 0.40 0.21                          4    0.06   0.29   0.79 11.23                                                                               0.082                                                                               1.57 0.26 0.11 0.20                          5    0.10   0.48   0.84 8.84 0.841                                                                               2.08 0.50 0.49 0.08                          6    0.25   0.74   0.70 12.33                                                                               0.250                                                                               0.38 0.26 0.48 0.05                          7    0.18   0.16   0.25 13.11                                                                               0.128                                                                               2.48 0.35 0.47 0.07                          8    0.14   0.56   0.55 15.41                                                                               0.301                                                                               2.87 0.60 0.15 0.10                          9    0.06   0.24   0.67 17.20                                                                               0.625                                                                               2.72 0.87 0.41 0.10                          10   0.20   0.27   0.47 9.83 0.427                                                                               1.44 0.50 0.44 0.15                          ______________________________________                                    

                  TABLE 1-2                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.    Ti       Zr     Ta     Hf  Co    Ni  Cu                                 ______________________________________                                         1      1.790    --     --     --  --    --  --                                 2      1.816    --     --     --  --    --  --                                 3      0.952    --     --     --  --    --  --                                 4      0.843    --     --     --  --    --  --                                 5      1.168    --     --     --  --    --  --                                 6      1.617    --     --     --  --    --  --                                 7      --       1.597  --     --  --    --  --                                 8      --       1.940  --     --  --    --  --                                 9      --       0.310  --     --  --    --  --                                 10     --       1.352  --     --  --    --  --                                 ______________________________________                                    

                  TABLE 1-3                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         1     0.0259  0.002    0.012                                                                               2       170    19                                  2     0.0013  0.002    0.003                                                                               2       135    26                                  3     0.0239  0.005    0.003                                                                               3       164    18                                  4     0.0151  0.004    0.018                                                                               4       133    15                                  5     0.0287  0.003    0.007                                                                               0       172    19                                  6     0.0155  0.008    0.015                                                                               1       158    24                                  7     0.0003  0.002    0.019                                                                               2       168    20                                  8     0.0229  0.003    0.006                                                                               1       180    20                                  9     0.0190  0.003    0.012                                                                               1       171    16                                  10    0.0280  0.004    0.014                                                                               2       171    20                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 2-1                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         11   0.22   0.49   0.64 17.23                                                                               0.050                                                                               3.46 0.30 0.41 0.21                          12   0.22   0.41   0.63 17.66                                                                               0.814                                                                               3.30 0.13 0.48 0.24                          13   0.15   0.28   0.32 15.59                                                                               0.078                                                                               2.05 0.79 0.07 0.09                          14   0.10   0.75   0.78 8.84 0.157                                                                               0.82 0.17 0.09 0.19                          15   0.17   0.52   0.67 14.68                                                                               0.395                                                                               2.36 0.55 0.47 0.15                          16   0.18   0.26   0.26 5.12 0.130                                                                               1.20 0.31 0.37 0.04                          17   0.07   0.21   0.22 10.58                                                                               0.199                                                                               1.75 0.27 0.46 0.19                          18   0.22   0.64   0.42 9.12 0.924                                                                               3.43 0.74 0.17 0.19                          19   0.17   0.64   0.73 11.97                                                                               0.665                                                                               0.80 0.11 0.15 0.13                          20   0.15   0.10   0.63 16.90                                                                               0.246                                                                               3.19 0.18 0.32 0.09                          21   0.25   0.03   0.36 15.00                                                                               0.487                                                                               1.78 0.76 0.35 0.15                          22   0.15   0.32   0.21 17.52                                                                               0.755                                                                               2.72 0.26 0.18 0.02                          23   0.07   0.46   0.84 15.56                                                                               0.858                                                                               0.42 0.45 0.44 0.04                          24   0.13   0.31   0.93 7.19 0.653                                                                               2.65 0.21 0.33 0.15                          25   0.13   0.53   0.34 16.17                                                                               0.961                                                                               0.58 0.34 0.24 0.09                          26   0.15   0.57   0.92 14.13                                                                               0.114                                                                               0.25 0.18 0.35 0.16                          27   0.02   0.74   0.08 12.43                                                                               0.972                                                                               1.21 0.10 0.35 0.22                          28   0.13   0.50   0.76 8.64 0.356                                                                               2.86 0.41 0.38 0.22                          29   0.12   0.51   0.94 7.18 0.102                                                                               1.35 0.44 0.36 0.25                          30   0.10   0.24   0.59 12.46                                                                               0.044                                                                               2.76 0.54 0.23 0.02                          31   0.03   0.73   0.37 15.70                                                                               0.017                                                                               1.57 0.54 0.13 0.09                          32   0.28   0.31   0.95 8.42 0.864                                                                               2.23 0.29 0.25 0.19                          33   0.24   0.40   0.20 7.98 0.920                                                                               2.52 0.60 0.24 0.15                          34   0.14   0.09   0.79 5.65 0.518                                                                               1.92 0.34 0.04 0.18                          35   0.23   0.43   1.00 12.41                                                                               0.496                                                                               3.17 0.80 0.04 0.12                          36   0.17   0.50   0.68 13.01                                                                               0.682                                                                               2.41 0.85 0.17 0.17                          37   0.05   0.57   0.50 11.87                                                                               0.915                                                                               2.43 0.81 0.36 0.16                          38   0.27   0.13   0.34 13.42                                                                               0.051                                                                               2.69 0.55 0.02 0.06                          39   0.05   0.21   0.87 8.96 0.896                                                                               2.65 0.86 0.06 0.07                          40   0.21   0.29   0.75 9.27 0.298                                                                               3.37 0.10 0.16 0.04                          ______________________________________                                    

                  TABLE 2-2                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.    Ti       Zr     Ta     Hf  Co    Ni  Cu                                 ______________________________________                                         11     --       1.738  --     --  --    --  --                                 12     --       1.155  --     --  --    --  --                                 13     0.139    1.257  --     --  --    --  --                                 14     1.612    1.716  --     --  --    --  --                                 15     1.252    0.233  --     --  --    --  --                                 16     1.732    0.455  --     --  --    --  --                                 17     1.697    0.052  --     --  --    --  --                                 18     0.825    1.705  --     --  --    --  --                                 19     --       --     0.095  --  --    --  --                                 20     --       --     0.340  --  --    --  --                                 21     --       --     0.989  --  --    --  --                                 22     --       --     0.779  --  --    --  --                                 23     --       --     1.339  --  --    --  --                                 24     --       --     0.354  --  --    --  --                                 25     0.981    --     0.498  --  --    --  --                                 26     1.649    --     1.420  --  --    --  --                                 27     0.561    --     1.818  --  --    --  --                                 28     1.351    --     1.373  --  --    --  --                                 29     1.702    --     1.729  --  --    --  --                                 30     1.288    --     1.569  --  --    --  --                                 31     --       0.689  0.535  --  --    --  --                                 32     --       1.635  1.354  --  --    --  --                                 33     --       0.709  0.668  --  --    --  --                                 34     --       1.582  1.156  --  --    --  --                                 35     --       1.931  0.482  --  --    --  --                                 36     --       1.429  0.321  --  --    --  --                                 37     1.355    1.736  1.335  --  --    --  --                                 38     1.996    1.543  0.220  --  --    --  --                                 39     0.922    0.512  0.631  --  --    --  --                                 40     1.786    1.310  0.238  --  --    --  --                                 ______________________________________                                    

                  TABLE 2-3                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         11    0.0156  0.009    0.009                                                                               1       156    25                                  12    0.0214  0.008    0.014                                                                               5       154    16                                  13    0.0106  0.008    0.015                                                                               5       143    22                                  14    0.0232  0.003    0.019                                                                               4       175    34                                  15    0.0246  0.001    0.013                                                                               1       179    18                                  16    0.0248  0.005    0.004                                                                               2       156    31                                  17    0.0037  0.004    0.016                                                                               5       135    20                                  18    0.0163  0.001    0.010                                                                               5       144    26                                  19    0.0278  0.005    0.020                                                                               2       135     8                                  20    0.0183  0.003    0.004                                                                               5       136     8                                  21    0.0129  0.009    0.007                                                                               6       150    14                                  22    0.0218  0.007    0.007                                                                               4       154    12                                  23    0.0247  0.010    0.001                                                                               4       177    20                                  24    0.0023  0.002    0.014                                                                               2       170    10                                  25    0.0090  0.004    0.006                                                                               0       162    17                                  26    0.0251  0.007    0.010                                                                               4       155    37                                  27    0.0161  0.004    0.015                                                                               3       152    26                                  28    0.0067  0.006    0.007                                                                               6       131    35                                  29    0.0219  0.009    0.013                                                                               0       145    38                                  30    0.0264  0.001    0.009                                                                               7       146    30                                  31    0.0163  0.004    0.012                                                                               6       162    17                                  32    0.0160  0.003    0.019                                                                               2       146    28                                  33    0.0207  0.009    0.008                                                                               2       175    24                                  34    0.0255  0.008    0.014                                                                               3       178    26                                  35    0.0107  0.007    0.004                                                                               0       131    27                                  36    0.0157  0.005    0.004                                                                               2       164    21                                  37    0.0061  0.009    0.012                                                                               4       177    41                                  38    0.0221  0.008    0.014                                                                               2       150    34                                  39    0.0284  0.002    0.008                                                                               1       135    29                                  40    0.0056  0.003    0.019                                                                               5       159    32                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M % : Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type       carbides in a weld heataffected zone                                     

                  TABLE 3-1                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         41   0.27   0.25   0.24 12.41                                                                               0.100                                                                               1.06 0.10 0.22 0.03                          42   0.05   0.35   0.43 16.05                                                                               0.123                                                                               1.77 0.19 0.18 0.01                          43   0.06   0.46   0.38 11.75                                                                               0.713                                                                               1.63 0.70 0.44 0.07                          44   0.26   0.45   0.74 10.09                                                                               0.699                                                                               1.78 0.50 0.19 0.15                          45   0.18   0.20   0.21 15.83                                                                               0.436                                                                               1.69 0.40 0.08 0.12                          46   0.05   0.36   0.65 13.54                                                                               0.736                                                                               2.41 0.24 0.26 0.15                          47   0.26   0.40   0.31 7.68 0.945                                                                               1.81 0.84 0.20 0.10                          48   0.04   0.60   0.69 15.73                                                                               0.411                                                                               0.98 0.58 0.27 0.17                          49   0.21   0.05   0.43 9.45 0.950                                                                               1.03 0.26 0.41 0.19                          50   0.15   0.17   0.21 12.60                                                                               0.411                                                                               3.05 0.23 0.30 0.25                          51   0.09   0.45   0.71 16.81                                                                               0.629                                                                               3.25 0.81 0.08 0.06                          52   0.13   0.37   0.58 13.24                                                                               0.932                                                                               1.02 0.36 0.43 0.08                          53   0.09   0.19   0.50 6.30 0.161                                                                               2.45 0.68 0.02 0.24                          54   0.19   0.17   0.72 13.28                                                                               0.645                                                                               0.39 0.15 0.01 0.17                          55   0.26   0.59   0.34 6.17 0.724                                                                               0.89 0.07 0.08 0.06                          56   0.23   0.12   0.41 8.81 0.740                                                                               1.79 0.78 0.13 0.23                          57   0.22   0.21   0.89 12.55                                                                               0.029                                                                               2.54 0.64 0.10 0.16                          58   0.17   0.74   0.97 15.27                                                                               0.420                                                                               0.94 0.48 0.15 0.17                          59   0.18   0.79   0.41 8.33 0.251                                                                               1.40 0.61 0.19 0.22                          60   0.20   0.64   0.57 9.10 0.855                                                                               3.36 0.89 0.39 0.04                          61   0.19   0.52   0.93 8.94 0.576                                                                               1.37 0.17 0.18 0.06                          62   0.09   0.72   0.55 5.73 0.246                                                                               1.46 0.74 0.22 0.12                          63   0.01   0.32   0.91 10.33                                                                               0.696                                                                               3.09 0.96 0.42 0.07                          64   0.04   0.37   0.28 7.70 0.776                                                                               2.45 0.69 0.22 0.10                          65   0.14   0.73   0.52 8.57 0.808                                                                               2.26 0.24 0.26 0.06                          66   0.11   0.50   0.29 10.86                                                                               0.136                                                                               1.99 0.94 0.23 0.03                          67   0.04   0.33   0.68 5.87 0.583                                                                               2.73 0.64 0.04 0.20                          68   0.19   0.49   0.74 17.63                                                                               0.505                                                                               0.69 0.67 0.34 0.18                          69   0.07   0.06   0.75 17.85                                                                               0.223                                                                               1.86 0.86 0.08 0.05                          70   0.20   0.46   0.56 17.30                                                                               0.563                                                                               2.43 0.56 0.16 0.24                          ______________________________________                                    

                  TABLE 3-2                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.    Ti       Zr     Ta     Hf  Co    Ni  Cu                                 ______________________________________                                         41     1.270    0.627  0.732  --  --    --  --                                 42     1.055    0.131  0.780  --  --    --  --                                 43     --       --     --     1.282                                                                              --    --  --                                 44     --       --     --     1.087                                                                              --    --  --                                 45     --       --     --     1.833                                                                              --    --  --                                 46     --       --     --     1.168                                                                              --    --  --                                 47     --       --     --     1.763                                                                              --    --  --                                 48     --       --     --     0.323                                                                              --    --  --                                 49     0.239    --     --     0.471                                                                              --    --  --                                 50     0.589    --     --     0.930                                                                              --    --  --                                 51     0.276    --     --     0.342                                                                              --    --  --                                 52     1.979    --     --     1.398                                                                              --    --  --                                 53     0.346    --     --     1.758                                                                              --    --  --                                 54     0.098    --     --     0.098                                                                              --    --  --                                 55     --       1.453  --     1.079                                                                              --    --  --                                 56     --       1.997  --     0.375                                                                              --    --  --                                 57     --       1.774  --     0.651                                                                              --    --  --                                 58     --       0.499  --     0.599                                                                              --    --  --                                 59     --       1.816  --     1.869                                                                              --    --  --                                 60     --       1.395  --     1.144                                                                              --    --  --                                 61     --       --     1.682  1.102                                                                              --    --  --                                 62     --       --     1.723  0.420                                                                              --    --  --                                 63     --       --     1.419  1.755                                                                              --    --  --                                 64     --       --     1.434  0.781                                                                              --    --  --                                 65     --       --     0.457  0.180                                                                              --    --  --                                 66     --       --     1.131  1.596                                                                              --    --  --                                 67     --       1.565  0.174  0.751                                                                              --    --  --                                 68     --       0.516  1.211  0.262                                                                              --    --  --                                 69     --       1.779  1.935  1.829                                                                              --    --  --                                 70     --       0.041  1.021  0.130                                                                              --    --  --                                 ______________________________________                                    

                  TABLE 3-3                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         41    0.0084  0.008    0.004                                                                               4       176    26                                  42    0.0168  0.003    0.002                                                                               2       163    23                                  43    0.0111  0.010    0.006                                                                               4       173    24                                  44    0.0161  0.002    0.006                                                                               1       133    19                                  45    0.0272  0.003    0.006                                                                               1       172    23                                  46    0.0091  0.002    0.005                                                                               0       142    22                                  47    0.0023  0.010    0.008                                                                               7       170    27                                  48    0.0016  0.007    0.003                                                                               1       160    10                                  49    0.0170  0.003    0.006                                                                               6       140    15                                  50    0.0142  0.003    0.004                                                                               4       136    17                                  51    0.0175  0.003    0.003                                                                               0       177    15                                  52    0.0076  0.005    0.011                                                                               0       166    35                                  53    0.0093  0.007    0.004                                                                               0       179    25                                  54    0.0026  0.004    0.009                                                                               2       171     7                                  55    0.0275  0.007    0.012                                                                               1       168    26                                  56    0.0193  0.003    0.011                                                                               3       149    29                                  57    0.0179  0.002    0.002                                                                               1       141    26                                  58    0.0034  0.003    0.020                                                                               2       171    16                                  59    0.0158  0.005    0.005                                                                               3       169    33                                  60    0.0205  0.002    0.001                                                                               6       160    32                                  61    0.0272  0.005    0.016                                                                               7       174    31                                  62    0.0167  0.005    0.017                                                                               4       162    28                                  63    0.0132  0.005    0.020                                                                               6       178    34                                  64    0.0122  0.002    0.003                                                                               6       149    31                                  65    0.0088  0.009    0.019                                                                               2       178    15                                  66    0.0128  0.002    0.020                                                                               7       168    30                                  67    0.0196  0.006    0.019                                                                               6       147    25                                  68    0.0090  0.003    0.005                                                                               5       142    26                                  69    0.0065  0.008    0.003                                                                               6       130    52                                  70    0.0216  0.002    0.009                                                                               1       141    23                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 4-1                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         71   0.12   0.04   0.47 14.15                                                                               0.389                                                                               1.88 0.59 0.25 0.25                          72   0.06   0.58   0.71 12.41                                                                               0.506                                                                               1.27 0.79 0.02 0.02                          73   0.26   0.03   0.80 16.86                                                                               0.283                                                                               1.78 0.03 0.14 0.13                          74   0.10   0.21   0.56 12.06                                                                               0.531                                                                               2.80 0.59 0.03 0.05                          75   0.25   0.60   0.29 9.07 0.105                                                                               0.55 0.35 0.34 0.22                          76   0.09   0.29   0.25 12.17                                                                               0.327                                                                               2.70 0.62 0.26 0.24                          77   0.29   0.70   0.30 12.77                                                                               0.044                                                                               0.48 0.26 0.45 0.08                          78   0.08   0.55   0.72 15.14                                                                               0.576                                                                               1.57 0.57 0.08 0.05                          79   0.29   0.10   0.58 10.74                                                                               0.275                                                                               0.50 0.91 0.31 0.24                          80   0.28   0.77   0.53 16.79                                                                               0.957                                                                               1.65 0.13 0.31 0.12                          81   0.30   0.10   0.45 11.82                                                                               0.476                                                                               1.20 0.04 0.01 0.13                          82   0.15   0.69   0.62 6.58 0.663                                                                               0.27 0.47 0.31 0.12                          83   0.08   0.46   0.89 11.99                                                                               0.845                                                                               1.58 0.77 0.38 0.05                          84   0.19   0.45   0.74 12.88                                                                               0.373                                                                               1.33 0.29 0.41 0.24                          85   0.28   0.15   0.43 7.25 0.577                                                                               0.62 0.35 0.30 0.04                          86   0.16   0.22   0.65 12.39                                                                               0.792                                                                               2.21 0.29 0.22 0.15                          87   0.08   0.12   0.84 13.14                                                                               0.855                                                                               2.25 0.93 0.34 0.15                          88   0.12   0.13   0.90 13.94                                                                               0.605                                                                               1.85 0.15 0.32 0.02                          89   0.25   0.11   0.66 12.44                                                                               0.861                                                                               0.44 0.72 0.10 0.18                          90   0.12   0.34   0.43 13.31                                                                               0.983                                                                               2.49 0.05 0.31 0.12                          91   0.26   0.27   0.44 7.63 0.289                                                                               2.44 0.40 0.16 0.17                          92   0.21   0.19   0.59 13.01                                                                               0.619                                                                               3.10 0.66 0.29 0.04                          93   0.04   0.74   0.33 14.16                                                                               0.316                                                                               0.61 0.16 0.37 0.05                          94   0.01   0.63   0.33 15.50                                                                               0.214                                                                               2.69 0.70 0.34 0.05                          95   0.21   0.11   0.47 8.31 0.632                                                                               0.49 0.16 0.09 0.11                          96   0.16   0.61   0.60 16.59                                                                               0.924                                                                               1.80 0.34 0.06 0.08                          97   0.25   0.07   0.21 5.61 0.424                                                                               1.06 0.59 0.14 0.03                          98   0.28   0.30   0.36 5.85 0.466                                                                               2.76 0.28 0.03 0.05                          99   0.21   0.80   0.53 8.72 0.893                                                                               1.38 0.69 0.38 0.21                          100  0.27   0.64   0.97 11.99                                                                               0.537                                                                               2.95 0.20 0.37 0.12                          ______________________________________                                    

                  TABLE 4-2                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.    Ti       Zr     Ta     Hf  Co    Ni  Cu                                 ______________________________________                                         71     --       0.959  0.136  0.829                                                                              --    --  --                                 72     --       0.207  1.931  0.576                                                                              --    --  --                                 73     1.690    --     0.124  1.077                                                                              --    --  --                                 74     1.669    --     1.346  1.982                                                                              --    --  --                                 75     1.132    --     0.292  0.976                                                                              --    --  --                                 76     0.733    --     1.636  0.741                                                                              --    --  --                                 77     1.144    --     1.047  0.932                                                                              --    --  --                                 78     1.047    --     0.175  1.207                                                                              --    --  --                                 79     1.103    1.777  --     0.273                                                                              --    --  --                                 80     1.962    1.910  --     1.785                                                                              --    --  --                                 81     1.337    1.417  --     0.404                                                                              --    --  --                                 82     0.868    0.962  --     0.806                                                                              --    --  --                                 83     1.253    0.256  --     0.676                                                                              --    --  --                                 84     1.139    0.928  --     1.675                                                                              --    --  --                                 85     0.236    0.671  0.100  0.467                                                                              --    --  --                                 86     1.171    0.156  0.291  0.738                                                                              --    --  --                                 87     0.654    0.051  0.247  1.156                                                                              --    --  --                                 88     1.329    1.029  0.669  0.394                                                                              --    --  --                                 89     0.872    1.763  0.209  0.132                                                                              --    --  --                                 90     1.956    1.935  1.548  1.028                                                                              --    --  --                                 91     1.262    --     --     --  0.63  --  --                                 92     1.455    --     --     --  4.01  --  --                                 93     1.218    --     --     --  3.88  --  --                                 94     0.200    --     --     --  1.89  --  --                                 95     0.077    --     --     --  2.04  --  --                                 96     1.534    --     --     --  1.15  --  --                                 97     --       1.537  --     --  3.24  --  --                                 98     --       0.293  --     --  2.57  --  --                                 99     --       0.537  --     --  3.35  --  --                                 100    --       0.912  --     --  2.34  --  --                                 ______________________________________                                    

                  TABLE 4-3                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         71    0.0049  0.001    0.012                                                                               7       150    23                                  72    0.0109  0.005    0.008                                                                               0       137    33                                  73    0.0202  0.006    0.013                                                                               6       179    35                                  74    0.0126  0.005    0.004                                                                               4       154    49                                  75    0.0286  0.003    0.008                                                                               4       138    30                                  76    0.0031  0.003    0.002                                                                               6       136    38                                  77    0.0058  0.010    0.002                                                                               1       149    29                                  78    0.0171  0.002    0.015                                                                               5       156    24                                  79    0.0022  0.002    0.017                                                                               7       160    35                                  80    0.0009  0.003    0.017                                                                               2       163    49                                  81    0.0081  0.004    0.019                                                                               2       142    30                                  82    0.0195  0.007    0.003                                                                               4       176    33                                  83    0.0295  0.008    0.002                                                                               3       142    28                                  84    0.0188  0.004    0.013                                                                               4       168    41                                  85    0.0119  0.007    0.006                                                                               3       131    22                                  86    0.0194  0.002    0.005                                                                               2       160    31                                  87    0.0208  0.002    0.017                                                                               3       157    30                                  88    0.0118  0.010    0.011                                                                               3       175    35                                  89    0.0024  0.005    0.001                                                                               2       167    37                                  90    0.0171  0.010    0.005                                                                               1       135    59                                  91    0.0213  0.008    0.018                                                                               5       157    17                                  92    0.0254  0.008    0.009                                                                               5       161    17                                  93    0.0089  0.008    0.004                                                                               4       175    16                                  94    0.0272  0.006    0.019                                                                               5       151     7                                  95    0.0007  0.007    0.002                                                                               7       167     8                                  96    0.0140  0.007    0.009                                                                               0       176    19                                  97    0.0172  0.002    0.015                                                                               2       155    24                                  98    0.0202  0.007    0.019                                                                               1       133    10                                  99    0.0036  0.007    0.009                                                                               2       161    12                                  100   0.0073  0.003    0.008                                                                               5       168    16                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 5-1                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         101  0.14   0.08   0.75 6.87 0.220                                                                               1.96 0.61 0.40 0.11                          102  0.20   0.19   0.95 11.03                                                                               0.298                                                                               2.89 0.29 0.41 0.12                          103  0.11   0.04   0.64 9.24 0.601                                                                               1.85 0.55 0.05 0.24                          104  0.26   0.67   0.88 5.76 0.456                                                                               1.61 0.25 0.01 0.19                          105  0.17   0.39   0.34 11.41                                                                               0.206                                                                               3.27 0.20 0.18 0.17                          106  0.07   0.27   0.49 17.82                                                                               0.686                                                                               1.33 0.24 0.48 0.14                          107  0.21   0.53   0.40 16.09                                                                               0.733                                                                               0.25 0.71 0.11 0.19                          108  0.26   0.30   0.73 17.14                                                                               0.675                                                                               1.06 0.46 0.19 0.14                          109  0.16   0.59   0.56 12.45                                                                               0.852                                                                               1.59 0.80 0.43 0.21                          110  0.17   0.12   0.55 6.22 0.109                                                                               1.35 0.11 0.23 0.12                          111  0.22   0.72   0.58 16.08                                                                               0.273                                                                               1.42 0.66 0.01 0.17                          112  0.27   0.29   0.51 7.19 0.686                                                                               2.91 0.35 0.43 0.23                          113  0.29   0.68   0.22 10.02                                                                               0.682                                                                               1.98 0.48 0.43 0.24                          114  0.21   0.18   0.37 9.45 0.098                                                                               1.38 0.89 0.41 0.16                          115  0.28   0.22   0.82 9.57 0.754                                                                               0.54 0.91 0.04 0.21                          116  0.16   0.68   0.64 14.96                                                                               0.993                                                                               0.59 0.41 0.23 0.20                          117  0.24   0.26   0.92 10.54                                                                               0.173                                                                               1.03 0.20 0.17 0.24                          118  0.04   0.79   0.31 7.23 0.613                                                                               2.93 0.60 0.26 0.04                          119  0.09   0.57   0.28 15.69                                                                               0.146                                                                               0.81 0.96 0.18 0.04                          120  0.06   0.27   0.71 8.04 0.121                                                                               0.75 0.16 0.09 0.20                          121  0.03   0.13   0.65 14.25                                                                               0.842                                                                               0.46 0.45 0.40 0.23                          122  0.25   0.02   0.78 6.38 0.170                                                                               2.77 0.71 0.29 0.23                          123  0.10   0.22   0.56 14.90                                                                               0.439                                                                               2.21 0.30 0.18 0.15                          124  0.25   0.22   0.69 5.34 0.500                                                                               3.21 0.05 0.24 0.19                          125  0.08   0.66   0.62 14.29                                                                               0.666                                                                               0.21 0.74 0.13 0.20                          126  0.11   0.23   0.20 7.25 0.295                                                                               2.62 0.28 0.26 0.13                          127  0.02   0.77   0.52 14.51                                                                               0.203                                                                               3.28 0.46 0.07 0.19                          128  0.03   0.58   0.25 7.90 0.724                                                                               3.29 0.63 0.21 0.21                          129  0.26   0.71   0.84 17.89                                                                               0.210                                                                               0.46 0.14 0.36 0.03                          130  0.21   0.64   0.58 9.84 0.986                                                                               2.52 0.78 0.18 0.11                          ______________________________________                                    

                  TABLE 5-2                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.    Ti       Zr     Ta     Hf  Co    Ni  Cu                                 ______________________________________                                         101    --       0.140  --     --  1.17  --  --                                 102    --       1.860  --     --  3.80  --  --                                 103    1.404    1.731  --     --  4.68  --  --                                 104    1.667    1.445  --     --  3.01  --  --                                 105    0.575    1.664  --     --  0.40  --  --                                 106    1.760    0.058  --     --  3.27  --  --                                 107    1.915    0.313  --     --  3.63  --  --                                 108    1.701    1.081  --     --  0.65  --  --                                 109    --       --     1.638  --  0.80  --  --                                 110    --       --     1.980  --  0.86  --  --                                 111    --       --     0.209  --  4.82  --  --                                 112    --       --     1.014  --  4.72  --  --                                 113    --       --     1.072  --  2.21  --  --                                 114    --       --     0.075  --  1.31  --  --                                 115    1.592    --     0.651  --  3.56  --  --                                 116    0.673    --     0.501  --  3.42  --  --                                 117    1.451    --     0.278  --  2.48  --  --                                 118    0.584    --     1.652  --  2.31  --  --                                 119    1.764    --     1.303  --  2.20  --  --                                 120    1.626    --     1.925  --  1.37  --  --                                 121    --       1.168  0.162  --  3.77  --  --                                 122    --       0.784  1.701  --  3.87  --  --                                 123    --       0.018  0.215  --  0.84  --  --                                 124    --       1.470  0.326  --  1.03  --  --                                 125    --       0.880  0.754  --  1.34  --  --                                 126    --       0.911  0.183  --  3.44  --  --                                 127    1.756    1.252  0.281  --  1.69  --  --                                 128    0.436    1.545  0.696  --  4.86  --  --                                 129    0.861    1.463  1.103  --  4.96  --  --                                 130    1.714    0.693  1.188  --  3.68  --  --                                 ______________________________________                                    

                  TABLE 5-3                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         101   0.0264  0.004    0.006                                                                               5       157     8                                  102   0.0258  0.001    0.007                                                                               5       155    21                                  103   0.0011  0.002    0.010                                                                               6       164    39                                  104   0.0216  0.004    0.019                                                                               0       164    22                                  105   0.0080  0.002    0.005                                                                               5       155    22                                  106   0.0298  0.008    0.010                                                                               0       167    23                                  107   0.0228  0.007    0.014                                                                               3       177    30                                  108   0.0264  0.006    0.003                                                                               6       162    33                                  109   0.0060  0.004    0.012                                                                               6       151    25                                  110   0.0016  0.004    0.019                                                                               1       146    24                                  111   0.0229  0.010    0.002                                                                               5       174    10                                  112   0.0058  0.009    0.015                                                                               0       139    17                                  113   0.0199  0.006    0.007                                                                               0       143    22                                  114   0.0155  0.009    0.005                                                                               6       164    12                                  115   0.0024  0.001    0.013                                                                               4       155    31                                  116   0.0209  0.009    0.010                                                                               6       168    15                                  117   0.0208  0.004    0.012                                                                               7       132    26                                  118   0.0271  0.003    0.005                                                                               3       149    28                                  119   0.0205  0.004    0.017                                                                               3       146    29                                  120   0.0107  0.010    0.015                                                                               0       152    39                                  121   0.0227  0.001    0.014                                                                               6       168    21                                  122   0.0219  0.009    0.003                                                                               1       174    27                                  123   0.0029  0.008    0.006                                                                               4       171    16                                  124   0.0205  0.002    0.001                                                                               1       137    27                                  125   0.0256  0.003    0.015                                                                               7       151    26                                  126   0.0134  0.005    0.005                                                                               5       164    16                                  127   0.0234  0.006    0.016                                                                               5       155    38                                  128   0.0210  0.005    0.018                                                                               6       151    26                                  129   0.0158  0.005    0.005                                                                               0       131    35                                  130   0.0185  0.009    0.004                                                                               7       146    37                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 6-1                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         131  0.14   0.64   0.53 7.51 0.891                                                                               2.28 0.93 0.09 0.03                          132  0.13   0.55   0.55 15.34                                                                               0.760                                                                               0.90 0.91 0.49 0.12                          133  0.28   0.28   0.92 11.68                                                                               0.928                                                                               2.74 0.07 0.09 0.21                          134  0.26   0.06   0.70 7.24 0.721                                                                               0.67 0.70 0.02 0.04                          135  0.16   0.18   0.56 6.61 0.491                                                                               2.41 0.19 0.20 0.03                          136  0.22   0.10   0.77 14.08                                                                               0.069                                                                               2.49 0.35 0.08 0.03                          137  0.12   0.10   0.81 14.55                                                                               0.288                                                                               0.33 0.52 0.05 0.25                          138  0.23   0.04   0.54 12.41                                                                               0.988                                                                               0.38 0.05 0.03 0.03                          139  0.23   0.20   0.63 5.54 0.016                                                                               2.09 0.74 0.20 0.07                          140  0.05   0.04   0.94 11.20                                                                               0.684                                                                               3.25 0.95 0.46 0.20                          141  0.24   0.61   0.95 14.26                                                                               0.833                                                                               1.64 0.54 0.25 0.15                          142  0.01   0.61   0.52 6.09 0.811                                                                               3.37 0.79 0.22 0.22                          143  0.06   0.30   0.33 17.26                                                                               0.956                                                                               1.30 0.10 0.30 0.04                          144  0.18   0.35   0.64 12.88                                                                               0.093                                                                               1.45 0.25 0.15 0.02                          145  0.04   0.62   0.93 10.57                                                                               0.068                                                                               1.69 0.12 0.20 0.15                          146  0.03   0.20   0.26 8.05 0.211                                                                               1.43 0.50 0.11 0.25                          147  0.09   0.12   0.89 9.42 0.336                                                                               1.72 0.26 0.03 0.04                          148  0.18   0.65   0.29 6.32 0.302                                                                               0.45 0.70 0.15 0.10                          149  0.11   0.12   0.34 9.76 0.454                                                                               0.40 0.71 0.38 0.13                          150  0.12   0.34   0.92 17.51                                                                               0.620                                                                               1.00 0.11 0.16 0.10                          151  0.02   0.79   0.27 14.38                                                                               0.136                                                                               1.70 0.70 0.37 0.09                          152  0.19   0.56   0.68 11.14                                                                               0.818                                                                               0.27 0.35 0.21 0.18                          153  0.16   0.31   0.81 5.80 0.037                                                                               1.20 0.39 0.33 0.10                          154  0.01   0.68   0.93 15.75                                                                               0.107                                                                               0.60 0.16 0.15 0.03                          155  0.15   0.39   0.51 12.78                                                                               0.363                                                                               1.23 0.95 0.34 0.18                          156  0.08   0.07   0.21 7.67 0.645                                                                               0.90 0.67 0.32 0.16                          157  0.04   0.78   0.32 17.99                                                                               0.293                                                                               0.72 0.61 0.26 0.16                          158  0.29   0.04   0.68 15.40                                                                               0.139                                                                               3.45 0.62 0.08 0.15                          159  0.18   0.07   0.38 10.97                                                                               0.022                                                                               0.30 0.04 0.18 0.20                          160  0.27   0.35   0.89 8.87 0.266                                                                               0.63 0.67 0.24 0.15                          ______________________________________                                    

                  TABLE 6-2                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.    Ti       Zr     Ta     Hf  Co    Ni  Cu                                 ______________________________________                                         131    0.647    1.902  1.623  --  4.99  --  --                                 132    1.348    1.760  0.077  --  3.27  --  --                                 133    --       --     --     0.962                                                                              4.97  --  --                                 134    --       --     --     1.168                                                                              4.50  --  --                                 135    --       --     --     1.762                                                                              1.05  --  --                                 136    --       --     --     0.437                                                                              3.44  --  --                                 137    --       --     --     1.831                                                                              1.30  --  --                                 138    --       --     --     0.643                                                                              1.01  --  --                                 139    0.032    --     --     0.561                                                                              4.23  --  --                                 140    0.020    --     --     1.225                                                                              0.56  --  --                                 141    0.800    --     --     0.314                                                                              3.59  --  --                                 142    0.091    --     --     1.513                                                                              0.57  --  --                                 143    0.542    --     --     1.455                                                                              2.60  --  --                                 144    1.809    --     --     1.849                                                                              1.78  --  --                                 145    --       1.395  --     1.367                                                                              4.55  --  --                                 146    --       0.851  --     0.674                                                                              0.52  --  --                                 147    --       1.029  --     0.440                                                                              0.85  --  --                                 148    --       1.604  --     0.336                                                                              4.77  --  --                                 149    --       1.249  --     0.028                                                                              4.27  --  --                                 150    --       1.610  --     1.176                                                                              0.97  --  --                                 151    --       --     1.696  0.475                                                                              1.32  --  --                                 152    --       --     0.524  1.620                                                                              4.58  --  --                                 153    --       --     0.473  0.262                                                                              0.29  --  --                                 154    --       --     1.208  1.053                                                                              2.06  --  --                                 155    --       --     1.419  0.689                                                                              1.93  --  --                                 156    --       --     1.769  0.830                                                                              1.48  --  --                                 157    --       1.492  0.925  1.141                                                                              2.35  --  --                                 158    --       0.991  1.568  0.313                                                                              1.35  --  --                                 159    --       1.284  1.367  0.995                                                                              4.86  --  --                                 160    --       0.032  1.984  1.878                                                                              4.93  --  --                                 ______________________________________                                    

                  TABLE 6-3                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         131   0.0237  0.006    0.003                                                                               0       174     1                                  132   0.0266  0.004    0.006                                                                               0       143    36                                  133   0.0078  0.006    0.013                                                                               3       132    16                                  134   0.0215  0.007    0.018                                                                               3       167    14                                  135   0.0033  0.004    0.001                                                                               7       177    25                                  136   0.0231  0.004    0.015                                                                               5       139    17                                  137   0.0011  0.008    0.019                                                                               5       131    26                                  138   0.0072  0.004    0.010                                                                               5       180    17                                  139   0.0217  0.003    0.004                                                                               7       164    19                                  140   0.0246  0.006    0.006                                                                               3       137    15                                  141   0.0111  0.009    0.015                                                                               6       176    22                                  142   0.0061  0.004    0.017                                                                               4       157    24                                  143   0.0191  0.010    0.009                                                                               4       161    29                                  144   0.0161  0.008    0.017                                                                               0       138    39                                  145   0.0220  0.006    0.009                                                                               6       167    36                                  146   0.0020  0.003    0.010                                                                               6       176    21                                  147   0.0254  0.009    0.018                                                                               2       167    16                                  148   0.0131  0.007    0.010                                                                               1       168    28                                  149   0.0196  0.007    0.001                                                                               1       131    19                                  150   0.0102  0.005    0.009                                                                               5       135    35                                  151   0.0251  0.006    0.020                                                                               5       157    28                                  152   0.0296  0.002    0.012                                                                               6       150    26                                  153   0.0184  0.008    0.011                                                                               6       142    13                                  154   0.0168  0.005    0.014                                                                               7       135    28                                  155   0.0048  0.006    0.007                                                                               1       132    26                                  156   0.0223  0.003    0.017                                                                               6       161    31                                  157   0.0196  0.009    0.001                                                                               4       174    36                                  158   0.0068  0.010    0.015                                                                               3       175    27                                  159   0.0233  0.007    0.016                                                                               5       141    42                                  160   0.0201  0.009    0.003                                                                               4       174    42                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 7-1                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         161  0.19   0.75   0.45 13.56                                                                               0.218                                                                               2.24 0.39 0.43 0.09                          162  0.21   0.37   0.97 16.56                                                                               0.721                                                                               2.96 0.02 0.43 0.10                          163  0.27   0.24   0.30 15.55                                                                               0.602                                                                               2.24 0.39 0.38 0.02                          164  0.18   0.63   0.7  08.38                                                                               0.691                                                                               2.83 0.35 0.47 0.04                          165  0.18   0.24   0.45 12.52                                                                               0.337                                                                               2.54 0.23 0.12 0.25                          166  0.23   0.10   0.21 6.25 0.857                                                                               0.80 0.83 0.46 0.25                          167  0.26   0.49   0.65 13.37                                                                               0.602                                                                               2.04 0.05 0.45 0.11                          168  0.25   0.49   0.85 12.46                                                                               0.906                                                                               2.46 0.19 0.26 0.05                          169  0.29   0.77   0.27 7.78 0.110                                                                               1.49 0.58 0.03 0.02                          170  0.18   0.40   0.78 16.70                                                                               0.537                                                                               0.22 0.58 0.43 0.10                          171  0.19   0.44   0.64 11.08                                                                               0.034                                                                               1.42 0.51 0.16 0.13                          172  0.20   0.75   0.54 8.30 0.926                                                                               2.89 0.21 0.10 0.20                          173  0.08   0.41   0.32 12.57                                                                               0.052                                                                               2.43 0.49 0.18 0.01                          174  0.07   0.49   0.27 15.46                                                                               0.749                                                                               1.19 0.73 0.08 0.15                          175  0.25   0.07   0.27 14.93                                                                               0.869                                                                               1.93 0.75 0.21 0.07                          176  0.30   0.59   0.56 8.71 0.735                                                                               0.79 0.39 0.24 0.11                          177  0.15   0.34   0.23 7.61 0.679                                                                               0.51 0.96 0.33 0.23                          178  0.05   0.78   0.73 16.09                                                                               0.047                                                                               2.23 0.83 0.41 0.03                          179  0.11   0.59   0.75 12.48                                                                               0.661                                                                               0.42 0.33 0.39 0.06                          180  0.12   0.05   0.54 14.09                                                                               0.366                                                                               2.83 0.76 0.44 0.17                          181  0.05   0.18   0.78 12.39                                                                               0.497                                                                               0.64 0.99 0.23 0.20                          182  0.13   0.48   0.93 5.14 0.880                                                                               1.55 0.36 0.42 0.10                          183  0.16   0.42   0.87 16.27                                                                               0.869                                                                               3.40 0.20 0.19 0.21                          184  0.11   0.66   0.86 11.14                                                                               0.788                                                                               2.33 0.81 0.45 0.11                          185  0.07   0.29   0.36 7.11 0.974                                                                               1.09 0.08 0.12 0.02                          186  0.14   0.74   0.86 15.01                                                                               0.764                                                                               2.46 0.80 0.12 0.12                          187  0.12   0.33   0.62 13.30                                                                               0.498                                                                               0.95 0.84 0.11 0.03                          188  0.26   0.09   0.30 12.80                                                                               0.503                                                                               0.93 0.04 0.27 0.07                          189  0.21   0.29   0.58 11.32                                                                               0.126                                                                               0.26 0.69 0.25 0.06                          190  0.09   0.80   0.93 13.34                                                                               0.694                                                                               1.68 0.18 0.49 0.22                          ______________________________________                                    

                  TABLE 7-2                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.    Ti       Zr     Ta     Hf  Co    Ni  Cu                                 ______________________________________                                         161    --       0.907  0.105  0.625                                                                              0.75  --  --                                 162    --       0.587  0.391  1.902                                                                              1.12  --  --                                 163    1.594    --     0.512  0.388                                                                              0.49  --  --                                 164    0.508    --     1.154  0.759                                                                              0.46  --  --                                 165    1.338    --     1.981  1.673                                                                              2.62  --  --                                 166    1.761    --     0.663  1.823                                                                              3.82  --  --                                 167    0.476    --     1.885  0.880                                                                              3.27  --  --                                 168    1.154    --     0.315  1.493                                                                              2.53  --  --                                 169    1.447    0.255  --     0.337                                                                              0.84  --  --                                 170    0.041    1.529  --     0.098                                                                              2.23  --  --                                 171    0.597    0.681  --     0.450                                                                              1.13  --  --                                 172    1.775    0.354  --     1.066                                                                              1.51  --  --                                 173    0.262    1.210  --     0.612                                                                              2.65  --  --                                 174    1.757    1.947  --     1.763                                                                              3.71  --  --                                 175    1.909    0.205  1.307  1.158                                                                              3.80  --  --                                 176    0.377    1.649  1.502  0.482                                                                              2.23  --  --                                 177    0.853    0.995  0.970  0.450                                                                              0.70  --  --                                 178    1.998    1.905  1.364  0.722                                                                              3.17  --  --                                 179    0.493    0.040  1.344  1.935                                                                              1.58  --  --                                 180    0.988    0.083  0.597  1.782                                                                              4.79  --  --                                 181    0.188    --     --     --  --    3.17                                                                               --                                 182    0.712    --     --     --  --    0.69                                                                               --                                 183    0.283    --     --     --  --    1.48                                                                               --                                 184    0.562    --     --     --  --    2.43                                                                               --                                 185    1.198    --     --     --  --    0.30                                                                               --                                 186    1.887    --     --     --  --    1.56                                                                               --                                 187    --       0.798  --     --  --    2.98                                                                               --                                 188    --       1.187  --     --  --    3.75                                                                               --                                 189    --       1.520  --     --  --    3.12                                                                               --                                 190    --       1.477  --     --  --    2.74                                                                               --                                 ______________________________________                                    

                  TABLE 7-3                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         161   0.0220  0.006    0.009                                                                               3       154    18                                  162   0.0238  0.004    0.003                                                                               4       156    34                                  163   0.0208  0.002    0.010                                                                               3       159    29                                  164   0.0230  0.003    0.009                                                                               4       142    33                                  165   0.0107  0.006    0.015                                                                               2       155    47                                  166   0.0088  0.010    0.005                                                                               3       178    44                                  167   0.0123  0.008    0.007                                                                               2       162    32                                  168   0.0162  0.007    0.006                                                                               5       137    33                                  169   0.0157  0.007    0.009                                                                               3       178    24                                  170   0.0062  0.006    0.005                                                                               0       165    27                                  171   0.0273  0.002    0.017                                                                               5       175    19                                  172   0.0294  0.008    0.014                                                                               2       135    37                                  173   0.0078  0.003    0.013                                                                               4       173    26                                  174   0.0170  0.010    0.019                                                                               6       143    50                                  175   0.0218  0.003    0.011                                                                               5       171    40                                  176   0.0029  0.004    0.013                                                                               2       161    44                                  177   0.0156  0.003    0.005                                                                               3       140    36                                  178   0.0098  0.003    0.010                                                                               3       137    57                                  179   0.0103  0.002    0.018                                                                               2       177    35                                  180   0.0120  0.002    0.013                                                                               2       165    37                                  181   0.0255  0.008    0.014                                                                               5       154     7                                  182   0.0009  0.009    0.017                                                                               2       145    12                                  183   0.0223  0.002    0.009                                                                               1       142    10                                  184   0.0260  0.001    0.015                                                                               2       173    12                                  185   0.0067  0.008    0.004                                                                               2       165    18                                  186   0.0192  0.004    0.010                                                                               6       145    23                                  187   0.0289  0.010    0.013                                                                               3       142    18                                  188   0.0008  0.006    0.017                                                                               6       134    23                                  189   0.0196  0.004    0.011                                                                               2       147    22                                  190   0.0209  0.008    0.019                                                                               2       135    19                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 8-1                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         191  0.27   0.33   0.81 10.22                                                                               0.553                                                                               1.33 0.31 0.39 0.14                          192  0.13   0.68   0.49 12.62                                                                               0.520                                                                               1.98 0.42 0.14 0.03                          193  0.05   0.18   0.64 12.12                                                                               0.945                                                                               1.44 0.36 0.13 0.09                          194  0.13   0.27   0.34 13.18                                                                               0.177                                                                               2.50 0.96 0.05 0.03                          195  0.04   0.41   0.65 13.48                                                                               0.033                                                                               1.27 0.56 0.05 0.18                          196  0.16   0.49   0.63 10.87                                                                               0.351                                                                               0.56 0.50 0.07 0.13                          197  0.30   0.37   0.56 16.37                                                                               0.473                                                                               3.09 0.60 0.01 0.10                          198  0.12   0.32   0.71 8.10 0.222                                                                               1.67 0.69 0.28 0.15                          199  0.15   0.58   0.92 16.48                                                                               0.429                                                                               2.40 0.13 0.32 0.01                          200  0.20   0.67   0.70 7.17 0.464                                                                               3.16 0.73 0.30 0.24                          201  0.23   0.44   0.70 16.85                                                                               0.149                                                                               3.36 0.86 0.37 0.09                          202  0.18   0.15   0.39 10.83                                                                               0.303                                                                               0.78 0.34 0.45 0.22                          203  0.16   0.46   0.44 13.07                                                                               0.771                                                                               1.49 0.98 0.47 0.13                          204  0.26   0.07   0.72 14.80                                                                               0.395                                                                               1.65 0.66 0.34 0.25                          205  0.29   0.80   0.69 7.58 0.508                                                                               0.75 0.69 0.23 0.18                          206  0.05   0.18   0.63 15.23                                                                               0.445                                                                               1.50 0.90 0.06 0.13                          207  0.08   0.42   0.40 9.31 0.031                                                                               1.73 0.65 0.23 0.05                          208  0.05   0.23   0.67 7.59 0.616                                                                               0.90 0.76 0.19 0.02                          209  0.04   0.66   0.52 14.30                                                                               0.038                                                                               1.78 0.57 0.33 0.02                          210  0.30   0.78   0.20 14.34                                                                               0.625                                                                               0.53 0.42 0.34 0.22                          211  0.20   0.08   0.80 11.98                                                                               0.714                                                                               1.52 0.12 0.36 0.13                          212  0.13   0.39   0.56 11.60                                                                               0.635                                                                               0.93 0.53 0.09 0.17                          213  0.20   0.41   0.98 17.71                                                                               0.248                                                                               1.56 0.99 0.18 0.07                          214  0.19   0.78   0.32 15.07                                                                               0.366                                                                               1.18 0.83 0.06 0.15                          215  0.08   0.22   0.84 7.95 0.323                                                                               2.51 0.39 0.12 0.01                          216  0.09   0.15   0.80 7.38 0.467                                                                               1.76 0.48 0.30 0.09                          217  0.05   0.44   0.49 11.21                                                                               0.633                                                                               1.71 0.48 0.27 0.11                          218  0.18   0.19   0.57 17.16                                                                               0.145                                                                               3.39 0.19 0.44 0.03                          219  0.15   0.05   0.91 10.31                                                                               0.857                                                                               1.41 0.95 0.24 0.18                          220  0.07   0.29   0.98 14.37                                                                               0.096                                                                               3.39 0.12 0.08 0.15                          ______________________________________                                    

                  TABLE 8-2                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.    Ti       Zr     Ta     Hf  Co    Ni  Cu                                 ______________________________________                                         191    --       0.724  --     --  --    4.15                                                                               --                                 192    --       0.919  --     --  --    4.15                                                                               --                                 193    1.414    1.737  --     --  --    1.99                                                                               --                                 194    1.662    1.868  --     --  --    4.10                                                                               --                                 195    1.995    0.968  --     --  --    4.86                                                                               --                                 196    0.112    0.729  --     --  --    1.15                                                                               --                                 197    0.652    1.798  --     --  --    4.10                                                                               --                                 198    0.270    1.867  --     --  --    0.94                                                                               --                                 199    --       --     1.997  --  --    0.51                                                                               --                                 200    --       --     1.618  --  --    4.42                                                                               --                                 201    --       --     0.590  --  --    2.15                                                                               --                                 202    --       --     0.612  --  --    0.32                                                                               --                                 203    --       --     0.376  --  --    2.88                                                                               --                                 204    --       --     0.521  --  --    1.81                                                                               --                                 205    1.236    --     1.723  --  --    3.54                                                                               --                                 206    0.913    --     1.670  --  --    2.48                                                                               --                                 207    1.757    --     0.032  --  --    0.25                                                                               --                                 208    0.433    --     1.456  --  --    3.23                                                                               --                                 209    0.603    --     0.634  --  --    1.05                                                                               --                                 210    0.952    --     1.214  --  --    2.47                                                                               --                                 211    --       1.529  0.895  --  --    4.41                                                                               --                                 212    --       0.011  0.342  --  --    1.20                                                                               --                                 213    --       0.565  0.231  --  --    1.71                                                                               --                                 214    --       0.844  1.209  --  --    2.64                                                                               --                                 215    --       0.545  1.976  --  --    0.98                                                                               --                                 216    --       0.338  1.198  --  --    2.99                                                                               --                                 217    0.551    0.877  1.540  --  --    3.18                                                                               --                                 218    1.440    0.847  0.689  --  --    0.69                                                                               --                                 219    0.559    1.905  1.286  --  --    2.00                                                                               --                                 220    1.563    0.76   0.050  --  --    1.47                                                                               --                                 ______________________________________                                    

                  TABLE 8-3                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         191   0.0145  0.002    0.001                                                                               7       151    16                                  192   0.0106  0.002    0.011                                                                               2       172    12                                  193   0.0041  0.009    0.016                                                                               1       176    30                                  194   0.0202  0.010    0.014                                                                               6       166    32                                  195   0.0238  0.009    0.002                                                                               1       144    29                                  196   0.0256  0.009    0.005                                                                               6       139    18                                  197   0.0051  0.008    0.011                                                                               3       177    24                                  198   0.0023  0.006    0.016                                                                               4       137    26                                  199   0.0126  0.005    0.007                                                                               2       147    24                                  200   0.0009  0.003    0.010                                                                               6       134    25                                  201   0.0218  0.003    0.004                                                                               7       175    14                                  202   0.0264  0.005    0.013                                                                               1       149    11                                  203   0.0097  0.003    0.015                                                                               4       159    15                                  204   0.0259  0.002    0.016                                                                               5       156    19                                  205   0.0108  0.008    0.015                                                                               3       170    33                                  206   0.0045  0.004    0.016                                                                               3       176    26                                  207   0.0165  0.007    0.007                                                                               0       180    25                                  208   0.0273  0.003    0.014                                                                               5       132    25                                  209   0.0019  0.003    0.015                                                                               5       161    16                                  210   0.0249  0.001    0.015                                                                               3       145    30                                  211   0.0022  0.005    0.012                                                                               4       161    25                                  212   0.0035  0.009    0.013                                                                               1       136    15                                  213   0.0086  0.002    0.004                                                                               3       150    12                                  214   0.0129  0.001    0.010                                                                               5       179    24                                  215   0.0118  0.010    0.011                                                                               2       176    33                                  216   0.0295  0.007    0.003                                                                               4       169    26                                  217   0.0022  0.006    0.010                                                                               3       160    37                                  218   0.0138  0.005    0.002                                                                               1       178    33                                  219   0.0153  0.007    0.013                                                                               0       150    35                                  220   0.0012  0.002    0.012                                                                               7       154    29                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 9-1                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         221  0.02   0.37   0.64 14.25                                                                               0.193                                                                               0.58 0.99 0.11 0.01                          222  0.25   0.18   0.97 14.38                                                                               0.985                                                                               2.32 0.46 0.27 0.23                          223  0.28   0.76   0.24 12.56                                                                               0.823                                                                               3.16 0.82 0.23 0.15                          224  0.06   0.03   0.70 13.02                                                                               0.518                                                                               2.47 0.41 0.14 0.21                          225  0.26   0.58   0.62 7.33 0.417                                                                               1.44 0.08 0.43 0.02                          226  0.26   0.35   0.30 12.90                                                                               0.374                                                                               2.84 0.16 0.03 0.01                          227  0.16   0.38   0.39 7.95 0.202                                                                               2.75 0.48 0.33 0.04                          228  0.06   0.14   0.34 16.35                                                                               0.737                                                                               2.34 0.38 0.27 0.04                          229  0.19   0.68   0.85 10.11                                                                               0.334                                                                               1.07 0.70 0.02 0.24                          230  0.22   0.32   0.98 6.50 0.315                                                                               3.32 0.29 0.22 0.23                          231  0.24   0.48   0.99 9.89 0.019                                                                               0.32 0.46 0.07 0.21                          232  0.22   0.65   0.35 11.64                                                                               0.776                                                                               3.05 0.55 0.22 0.14                          233  0.10   0.30   0.93 9.52 0.421                                                                               2.71 0.39 0.33 0.21                          234  0.26   0.48   1.00 14.56                                                                               0.306                                                                               0.47 0.34 0.10 0.16                          235  0.09   0.28   0.83 5.06 0.252                                                                               2.34 0.22 0.41 0.06                          236  0.25   0.36   0.69 11.45                                                                               0.104                                                                               1.20 0.86 0.21 0.12                          237  0.13   0.19   0.84 11.98                                                                               0.189                                                                               1.44 0.62 0.39 0.16                          238  0.25   0.04   0.76 11.14                                                                               0.848                                                                               0.89 0.81 0.40 0.05                          239  0.13   0.17   0.31 13.18                                                                               0.418                                                                               0.63 0.78 0.38 0.08                          240  0.15   0.06   0.97 9.52 0.730                                                                               1.79 0.38 0.01 0.23                          241  0.14   0.37   0.59 11.08                                                                               0.132                                                                               0.52 0.40 0.20 0.22                          242  0.17   0.56   0.66 9.08 0.438                                                                               1.24 0.23 0.13 0.12                          243  0.22   0.15   0.64 8.14 0.510                                                                               1.77 0.17 0.22 0.02                          244  0.22   0.54   0.79 5.96 0.671                                                                               1.54 0.56 0.12 0.24                          245  0.27   0.44   0.99 6.88 0.754                                                                               1.67 0.25 0.26 0.01                          246  0.05   0.51   0.31 8.74 0.595                                                                               1.62 0.07 0.06 0.03                          247  0.21   0.61   0.60 15.93                                                                               0.528                                                                               2.46 0.34 0.17 0.12                          248  0.15   0.23   0.96 13.52                                                                               0.402                                                                               2.07 0.42 0.28 0.14                          249  0.10   0.79   0.43 5.61 0.046                                                                               3.16 0.14 0.06 0.03                          250  0.15   0.24   0.89 16.22                                                                               0.789                                                                               0.26 0.81 0.40 0.13                          ______________________________________                                    

                  TABLE 9-2                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         221  0.118    1.041  0.597  --   --     0.72 --                                222  0.915    0.451  1.641  --   --     1.38 --                                223  --       --     --     0.338                                                                               --     2.68 --                                224  --       --     --     0.103                                                                               --     3.76 --                                225  --       --     --     0.754                                                                               --     1.52 --                                226  --       --     --     0.945                                                                               --     2.34 --                                227  --       --     --     0.339                                                                               --     0.58 --                                228  --       --     --     1.617                                                                               --     2.73 --                                229  0.410    --     --     0.455                                                                               --     3.20 --                                230  0.260    --     --     0.507                                                                               --     1.13 --                                231  0.398    --     --     1.461                                                                               --     0.59 --                                232  1.468    --     --     1.955                                                                               --     3.11 --                                233  0.153    --     --     1.729                                                                               --     3.26 --                                234  0.146    --     --     0.403                                                                               --     4.91 --                                235  --       0.893  --     0.643                                                                               --     4.92 --                                236  --       1.458  --     0.163                                                                               --     2.55 --                                237  --       1.227  --     1.607                                                                               --     1.75 --                                238  --       0.846  --     0.642                                                                               --     4.15 --                                239  --       1.017  --     1.958                                                                               --     4.18 --                                240  --       0.399  --     0.226                                                                               --     1.03 --                                241  --       --     1.741  0.097                                                                               --     3.51 --                                242  --       --     1.531  0.248                                                                               --     1.25 --                                243  --       --     1.912  1.371                                                                               --     0.65 --                                244  --       --     0.554  0.116                                                                               --     3.33 --                                245  --       --     0.145  0.176                                                                               --     1.31 --                                246  --       --     0.350  0.219                                                                               --     3.42 --                                247  --       0.335  1.823  0.900                                                                               --     1.63 --                                248  --       0.570  0.249  1.891                                                                               --     4.74 --                                249  --       1.069  1.298  0.885                                                                               --     4.80 --                                250  --       0.499  0.648  0.540                                                                               --     1.04 --                                ______________________________________                                    

                  TABLE 9-3                                                        ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         221   0.0120  0.010    0.006                                                                               2       168    20                                  222   0.0271  0.003    0.018                                                                               6       143    32                                  223   0.0277  0.007    0.009                                                                               3       159     9                                  224   0.0230  0.006    0.014                                                                               3       168    13                                  225   0.0086  0.004    0.019                                                                               4       147    18                                  226   0.0089  0.009    0.002                                                                               2       174    19                                  227   0.0194  0.004    0.009                                                                               3       177    10                                  228   0.0204  0.008    0.016                                                                               2       134    26                                  229   0.0067  0.004    0.002                                                                               2       173    18                                  230   0.0034  0.009    0.011                                                                               0       170    17                                  231   0.0054  0.008    0.012                                                                               4       180    28                                  232   0.0227  0.010    0.020                                                                               1       179    36                                  233   0.0212  0.002    0.013                                                                               1       170    29                                  234   0.0099  0.003    0.016                                                                               7       132    18                                  235   0.0147  0.005    0.018                                                                               6       142    24                                  236   0.0153  0.008    0.014                                                                               4       177    19                                  237   0.0220  0.006    0.012                                                                               0       165    33                                  238   0.0147  0.009    0.017                                                                               4       160    25                                  239   0.0184  0.005    0.018                                                                               4       138    29                                  240   0.0283  0.004    0.020                                                                               3       153    13                                  241   0.0096  0.004    0.010                                                                               2       157    26                                  242   0.0171  0.001    0.015                                                                               0       178    19                                  243   0.0012  0.006    0.011                                                                               1       169    37                                  244   0.0164  0.004    0.007                                                                               5       157    15                                  245   0.0286  0.003    0.016                                                                               6       170     9                                  246   0.0176  0.010    0.009                                                                               5       136    14                                  247   0.0082  0.010    0.018                                                                               1       133    33                                  248   0.0253  0.002    0.004                                                                               1       139    31                                  249   0.0195  0.002    0.012                                                                               2       155    34                                  250   0.0158  0.008    0.018                                                                               4       161    25                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 10-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         251  0.12   0.76   0.21 17.18                                                                               0.976                                                                               1.07 0.81 0.49 0.03                          252  0.10   0.30   0.26 12.84                                                                               0.941                                                                               3.40 0.46 0.01 0.05                          253  0.04   0.26   0.90 13.98                                                                               0.512                                                                               3.38 0.57 0.34 0.15                          254  0.05   0.54   0.82 5.66 0.537                                                                               0.52 1.00 0.19 0.06                          255  0.21   0.61   0.25 11.51                                                                               0.332                                                                               2.45 0.09 0.19 0.09                          256  0.20   0.73   0.69 16.68                                                                               0.764                                                                               0.51 0.65 0.04 0.21                          257  0.25   0.40   0.41 12.40                                                                               0.647                                                                               2.29 0.43 0.12 0.25                          258  0.18   0.63   0.46 15.82                                                                               0.315                                                                               2.32 0.10 0.39 0.18                          259  0.07   0.15   0.33 12.23                                                                               0.620                                                                               1.77 0.15 0.49 0.07                          260  0.17   0.77   0.67 12.23                                                                               0.886                                                                               1.68 0.52 0.11 0.02                          261  0.30   0.03   0.95 13.70                                                                               0.948                                                                               1.55 0.57 0.39 0.09                          262  0.25   0.13   0.66 14.65                                                                               0.159                                                                               0.84 0.13 0.03 0.01                          263  0.12   0.57   0.85 6.34 0.834                                                                               0.64 0.02 0.42 0.22                          264  0.02   0.03   0.99 12.60                                                                               0.319                                                                               0.38 0.09 0.25 0.20                          265  0.18   0.73   0.95 11.85                                                                               0.441                                                                               2.87 0.65 0.17 0.03                          266  0.12   0.21   1.00 8.44 0.550                                                                               0.95 0.08 0.35 0.04                          267  0.23   0.67   0.21 6.70 0.468                                                                               0.67 0.19 0.22 0.05                          268  0.02   0.05   0.84 11.14                                                                               0.047                                                                               1.52 0.31 0.19 0.04                          269  0.04   0.55   0.78 6.58 0.613                                                                               2.94 0.30 0.19 0.08                          270  0.08   0.09   0.29 10.30                                                                               0.502                                                                               2.72 0.47 0.36 0.14                          271  0.09   0.10   0.82 7.14 0.545                                                                               0.32 0.66 0.15 0.17                          272  0.04   0.46   0.65 8.10 0.588                                                                               1.81 0.23 0.44 0.01                          273  0.02   0.26   0.86 10.97                                                                               0.960                                                                               3.38 0.98 0.20 0.11                          274  0.27   0.16   0.92 13.67                                                                               0.010                                                                               1.15 0.78 0.30 0.19                          275  0.16   0.79   0.67 13.99                                                                               0.551                                                                               1.18 0.94 0.19 0.09                          276  0.08   0.48   0.41 9.82 0.933                                                                               2.93 0.82 0.26 0.12                          277  0.13   0.27   0.39 5.54 0.494                                                                               0.92 0.73 0.21 0.13                          278  0.11   0.41   0.89 5.52 0.563                                                                               2.83 0.52 0.18 0.08                          279  0.27   0.79   0.97 7.62 0.973                                                                               3.21 0.53 0.34 0.05                          280  0.27   0.10   0.50 16.16                                                                               0.574                                                                               1.50 0.09 0.13 0.11                          ______________________________________                                    

                  TABLE 10-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         251  --       1.532  1.968  1.534                                                                               --     2.25 --                                252  --       1.831  0.924  1.529                                                                               --     0.42 --                                253  0.803    --     1.189  1.203                                                                               --     1.98 --                                254  1.794    --     0.446  1.234                                                                               --     3.76 --                                255  1.178    --     1.347  0.282                                                                               --     4.92 --                                256  0.669    --     1.568  0.006                                                                               --     2.30 --                                257  1.865    --     1.787  0.110                                                                               --     2.35 --                                258  1.510    --     1.686  1.249                                                                               --     4.24 --                                259  0.248    0.985  --     1.109                                                                               --     2.42 --                                260  0.747    1.654  --     0.344                                                                               --     3.26 --                                261  0.690    1.627  --     0.621                                                                               --     3.56 --                                262  0.733    0.594  --     0.632                                                                               --     2.61 --                                263  1.562    1.228  --     0.042                                                                               --     4.34 --                                264  1.829    0.192  --     1.507                                                                               --     0.81 --                                265  0.239    0.167  0.176  1.724                                                                               --     0.82 --                                266  0.432    0.819  0.623  0.357                                                                               --     1.19 --                                267  1.083    1.821  0.789  1.070                                                                               --     1.12 --                                268  1.896    1.854  0.352  0.550                                                                               --     2.25 --                                269  0.526    1.566  0.959  1.438                                                                               --     1.33 --                                270  1.625    0.646  0.293  0.424                                                                               --     4.80 --                                271  0.875    --     --     --   4.92   4.72 --                                272  1.948    --     --     --   1.30   2.68 --                                273  0.540    --     --     --   1.21   0.25 --                                274  0.300    --     --     --   3.89   1.47 --                                275  1.883    --     --     --   1.33   0.73 --                                276  0.993    --     --     --   4.81   2.10 --                                277  --       1.883  --     --   1.49   2.39 --                                278  --       1.083  --     --   2.60   3.16 --                                279  --       1.692  --     --   4.94   1.25 --                                280  --       0.390  --     --   0.53   3.06 --                                ______________________________________                                    

                  TABLE 10-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         251   0.0093  0.002    0.019                                                                               6       158    51                                  252   0.0095  0.004    0.003                                                                               6       174    45                                  253   0.0271  0.009    0.015                                                                               4       137    31                                  254   0.0121  0.005    0.004                                                                               2       176    33                                  255   0.0193  0.006    0.004                                                                               1       166    28                                  256   0.0288  0.008    0.013                                                                               2       162    31                                  257   0.0210  0.007    0.017                                                                               5       141    36                                  258   0.0208  0.006    0.015                                                                               1       156    47                                  259   0.0233  0.007    0.002                                                                               4       134    30                                  260   0.0086  0.004    0.004                                                                               4       154    31                                  261   0.0164  0.006    0.018                                                                               6       142    29                                  262   0.0124  0.005    0.012                                                                               2       177    23                                  263   0.0212  0.006    0.012                                                                               1       137    36                                  264   0.0232  0.006    0.005                                                                               6       148    38                                  265   0.0132  0.004    0.008                                                                               5       140    27                                  266   0.0018  0.007    0.006                                                                               4       139    22                                  267   0.0133  0.002    0.017                                                                               2       173    44                                  268   0.0283  0.003    0.008                                                                               4       146    48                                  269   0.0116  0.002    0.015                                                                               3       134    41                                  270   0.0186  0.004    0.015                                                                               5       141    37                                  271   0.0142  0.009    0.006                                                                               0       144    19                                  272   0.0086  0.002    0.012                                                                               6       172    29                                  273   0.0114  0.004    0.002                                                                               4       151    12                                  274   0.0184  0.009    0.011                                                                               3       159     9                                  275   0.0239  0.005    0.016                                                                               6       150    22                                  276   0.0087  0.007    0.006                                                                               4       150    14                                  277   0.0127  0.002    0.006                                                                               4       164    21                                  278   0.0157  0.003    0.003                                                                               0       168    15                                  279   0.0279  0.008    0.002                                                                               3       140    23                                  280   0.0296  0.003    0.002                                                                               3       157    11                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 11-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         281  0.21   0.16   0.55 9.60 0.692                                                                               0.45 0.04 0.45 0.24                          282  0.04   0.07   1.00 11.83                                                                               0.171                                                                               1.18 0.69 0.47 0.03                          283  0.15   0.09   0.50 14.04                                                                               0.827                                                                               1.50 0.42 0.37 0.05                          284  0.05   0.48   0.93 7.76 0.514                                                                               0.83 0.03 0.06 0.24                          285  0.13   0.33   0.95 16.76                                                                               0.069                                                                               0.36 0.37 0.20 0.10                          286  0.20   0.30   0.84 13.00                                                                               0.319                                                                               1.12 0.28 0.46 0.06                          287  0.07   0.65   0.86 13.75                                                                               0.599                                                                               2.61 0.10 0.27 0.21                          288  0.13   0.07   0.49 10.48                                                                               0.256                                                                               2.63 0.64 0.29 0.02                          289  0.03   0.40   0.39 7.51 0.118                                                                               2.29 0.27 0.19 0.06                          290  0.17   0.72   0.43 15.69                                                                               0.023                                                                               1.04 0.79 0.38 0.04                          291  0.20   0.13   0.48 6.91 0.801                                                                               1.64 0.08 0.29 0.18                          292  0.08   0.05   0.80 17.97                                                                               0.794                                                                               0.25 0.43 0.32 0.17                          293  0.05   0.36   0.87 7.79 0.338                                                                               2.92 0.21 0.41 0.24                          294  0.07   0.15   0.95 13.30                                                                               0.768                                                                               2.54 0.73 0.47 0.10                          295  0.22   0.08   0.52 6.30 0.424                                                                               1.85 0.35 0.41 0.06                          296  0.18   0.40   0.65 17.17                                                                               0.631                                                                               0.29 0.39 0.17 0.22                          297  0.19   0.21   0.79 17.72                                                                               0.737                                                                               2.30 0.20 0.39 0.16                          298  0.20   0.55   0.42 12.37                                                                               0.565                                                                               2.34 0.59 0.25 0.10                          299  0.15   0.51   0.61 11.99                                                                               0.964                                                                               3.24 0.42 0.41 0.11                          300  0.16   0.74   0.43 14.49                                                                               0.270                                                                               2.76 0.04 0.31 0.03                          301  0.02   0.34   0.54 17.69                                                                               0.808                                                                               2.03 0.73 0.35 0.19                          302  0.13   0.75   0.43 6.51 0.925                                                                               0.51 0.88 0.21 0.18                          303  0.29   0.64   0.34 11.22                                                                               0.948                                                                               2.58 0.81 0.05 0.08                          304  0.15   0.30   0.56 16.62                                                                               0.212                                                                               1.09 0.84 0.27 0.22                          305  0.27   0.76   0.55 7.85 0.066                                                                               2.15 0.82 0.32 0.08                          306  0.15   0.73   0.98 8.57 0.328                                                                               0.23 0.59 0.10 0.08                          307  0.17   0.07   0.90 16.38                                                                               0.324                                                                               1.35 0.49 0.02 0.09                          308  0.15   0.21   1.00 16.52                                                                               0.413                                                                               3.37 0.79 0.02 0.17                          309  0.19   0.26   0.36 7.00 0.945                                                                               0.84 0.92 0.50 0.17                          310  0.09   0.10   0.43 11.53                                                                               0.243                                                                               3.12 0.70 0.40 0.06                          ______________________________________                                    

                  TABLE 11-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         281  --       1.822  --     --   0.53   0.58 --                                282  --       0.712  --     --   4.25   2.69 --                                283  0.574    0.683  --     --   1.21   3.71 --                                284  1.971    1.393  --     --   2.64   0.50 --                                285  0.951    0.559  --     --   0.57   4.25 --                                286  0.147    1.851  --     --   1.46   2.28 --                                287  1.251    1.941  --     --   2.12   0.94 --                                288  1.925    0.495  --     --   1.71   1.80 --                                289  --       --     0.602  --   4.25   1.71 --                                290  --       --     0.709  --   4.21   4.71 --                                291  --       --     0.651  --   3.13   0.35 --                                292  --       --     1.113  --   0.25   4.68 --                                293  --       --     1.738  --   1.96   2.45 --                                294  --       --     0.233  --   0.29   2.57 --                                295  1.277    --     1.252  --   4.05   4.16 --                                296  1.752    --     1.482  --   0.48   1.73 --                                297  1.867    --     1.586  --   0.75   1.61 --                                298  0.258    --     1.229  --   4.10   3.06 --                                299  1.616    --     0.091  --   4.93   0.46 --                                300  1.633    --     1.842  --   2.47   2.65 --                                301  --       0.207  0.156  --   0.70   4.02 --                                302  --       0.750  0.712  --   3.68   1.40 --                                303  --       0.823  1.165  --   0.99   1.22 --                                304  --       1.106  1.196  --   1.43   0.25 --                                305  --       0.272  1.475  --   1.84   4.92 --                                306  --       0.980  1.667  --   1.38   4.80 --                                307  0.959    1.913  1.452  --   4.15   3.97 --                                308  0.239    1.730  1.484  --   2.05   1.60 --                                309  0.234    0.142  0.479  --   1.62   4.15 --                                310  0.586    0.789  1.078  --   4.41   1.21 --                                ______________________________________                                    

                  TABLE 11-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         281   0.0006  0.008    0.018                                                                               3       149    19                                  282   0.0259  0.009    0.019                                                                               6       142    19                                  283   0.0106  0.004    0.010                                                                               7       139    17                                  284   0.0248  0.009    0.018                                                                               4       167    39                                  285   0.0186  0.006    0.010                                                                               4       131    19                                  286   0.0028  0.010    0.012                                                                               6       156    28                                  287   0.0166  0.006    0.012                                                                               1       172    36                                  288   0.0106  0.008    0.015                                                                               5       156    29                                  289   0.0243  0.008    0.010                                                                               1       134    17                                  290   0.0235  0.009    0.012                                                                               1       137    10                                  291   0.0029  0.007    0.017                                                                               3       140    13                                  292   0.0171  0.007    0.004                                                                               7       172    15                                  293   0.0018  0.009    0.009                                                                               4       160    20                                  294   0.0268  0.003    0.017                                                                               4       133    16                                  295   0.0125  0.004    0.016                                                                               3       167    34                                  296   0.0286  0.007    0.014                                                                               1       141    38                                  297   0.0256  0.002    0.015                                                                               6       133    31                                  298   0.0133  0.009    0.009                                                                               6       169    18                                  299   0.0016  0.009    0.019                                                                               6       179    21                                  300   0.0008  0.009    0.005                                                                               6       139    41                                  301   0.0209  0.008    0.002                                                                               4       177    15                                  302   0.0271  0.009    0.016                                                                               2       171    17                                  303   0.0147  0.006    0.015                                                                               0       174    22                                  304   0.0232  0.003    0.007                                                                               0       164    28                                  305   0.0032  0.005    0.015                                                                               4       143    26                                  306   0.0239  0.004    0.009                                                                               1       139    33                                  307   0.0065  0.006    0.005                                                                               2       180    40                                  308   0.0204  0.006    0.018                                                                               1       143    33                                  309   0.0012  0.006    0.008                                                                               7       131    14                                  310   0.0183  0.002    0.018                                                                               0       172    31                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 12-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         311  0.10   0.74   0.29 14.89                                                                               0.132                                                                               1.34 0.43 0.12 0.14                          312  0.03   0.13   0.20 8.54 0.953                                                                               3.26 0.95 0.33 0.14                          313  0.10   0.47   0.84 16.34                                                                               0.552                                                                               1.73 0.14 0.45 0.03                          314  0.29   0.07   0.46 10.07                                                                               0.749                                                                               2.80 0.77 0.41 0.23                          315  0.24   0.76   0.95 7.19 0.887                                                                               2.62 0.23 0.11 0.24                          316  0.21   0.05   0.56 5.37 0.799                                                                               2.30 0.31 0.45 0.25                          317  0.14   0.18   0.76 15.68                                                                               0.326                                                                               2.95 0.87 0.40 0.22                          318  0.28   0.62   0.63 16.48                                                                               0.800                                                                               0.76 0.26 0.34 0.24                          319  0.14   0.06   0.44 12.09                                                                               0.065                                                                               3.41 0.30 0.44 0.02                          320  0.26   0.35   0.84 6.87 0.444                                                                               2.10 0.81 0.14 0.12                          321  0.15   0.56   0.52 11.65                                                                               0.278                                                                               2.91 0.67 0.09 0.16                          322  0.21   0.56   0.54 17.85                                                                               0.403                                                                               0.32 0.67 0.45 0.19                          323  0.23   0.24   0.36 10.32                                                                               0.656                                                                               0.43 0.67 0.16 0.08                          324  0.17   0.63   0.67 6.44 0.375                                                                               1.02 0.50 0.37 0.13                          325  0.29   0.05   0.52 17.17                                                                               0.401                                                                               1.58 0.51 0.27 0.07                          326  0.08   0.31   0.99 14.24                                                                               0.060                                                                               1.53 0.03 0.50 0.10                          327  0.23   0.12   0.74 15.10                                                                               0.691                                                                               2.00 0.37 0.50 0.06                          328  0.26   0.52   0.84 11.02                                                                               0.629                                                                               0.79 0.88 0.18 0.03                          329  0.26   0.22   0.77 12.93                                                                               0.212                                                                               0.64 0.41 0.44 0.21                          330  0.19   0.25   0.38 5.69 0.273                                                                               1.06 0.29 0.48 0.21                          331  0.28   0.09   0.35 13.06                                                                               0.640                                                                               1.43 0.84 0.45 0.09                          332  0.21   0.40   0.95 13.62                                                                               0.668                                                                               2.94 0.91 0.28 0.07                          333  0.21   0.67   0.85 11.63                                                                               0.684                                                                               3.36 0.85 0.36 0.09                          334  0.23   0.36   0.31 11.46                                                                               0.026                                                                               0.51 0.97 0.39 0.14                          335  0.09   0.54   0.81 17.53                                                                               0.522                                                                               0.44 0.13 0.03 0.04                          336  0.03   0.66   0.61 8.04 0.019                                                                               2.60 0.15 0.43 0.23                          337  0.28   0.62   0.37 6.98 0.339                                                                               1.51 0.85 0.03 0.20                          338  0.22   0.67   0.78 12.20                                                                               0.327                                                                               1.57 0.10 0.24 0.14                          339  0.10   0.29   0.90 8.67 0.824                                                                               2.27 0.71 0.47 0.03                          340  0.15   0.53   0.60 7.17 0.663                                                                               3.05 0.54 0.40 0.17                          ______________________________________                                    

                  TABLE 12-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         311  1.965    0.352  1.955  --   2.43   3.98 --                                312  0.054    0.505  1.795  --   4.50   2.06 --                                313  --       --     --     1.693                                                                               0.23   4.31 --                                314  --       --     --     1.243                                                                               0.81   0.29 --                                315  --       --     --     0.129                                                                               3.07   3.63 --                                316  --       --     --     0.034                                                                               1.47   3.98 --                                317  --       --     --     0.616                                                                               4.78   0.50 --                                318  --       --     --     1.532                                                                               2.57   2.03 --                                319  1.707    --     --     0.482                                                                               1.32   2.97 --                                320  1.592    --     --     1.121                                                                               2.61   2.54 --                                321  1.218    --     --     1.121                                                                               3.243  4.73 --                                322  0.266    --     --     0.167                                                                               2.46   3.99 --                                323  1.393    --     --     1.917                                                                               1.86   4.32 --                                324  0.313    --     --     1.054                                                                               3.06   2.51 --                                325  --       0.257  --     0.237                                                                               0.45   4.98 --                                326  --       1.130  --     1.148                                                                               2.86   3.76 --                                327  --       0.652  --     0.44 4.71   2.88 --                                328  --       1.522  --     0.823                                                                               2.82   1.52 --                                329  --       1.408  --     1.947                                                                               3.61   1.32 --                                330  --       0.965  --     0.483                                                                               3.85   3.85 --                                331  --       --     1.949  1.098                                                                               2.78   1.15 --                                332  --       --     1.906  1.463                                                                               1.98   1.98 --                                333  --       --     0.919  0.267                                                                               3.09   0.85 --                                334  --       --     1.668  0.168                                                                               0.56   1.74 --                                335  --       --     1.800  0.808                                                                               3.05   3.71 --                                336  --       --     0.987  1.876                                                                               0.29   1.33 --                                337  --       0.199  0.960  1.110                                                                               1.18   1.10 --                                338  --       1.373  1.368  1.138                                                                               4.86   2.12 --                                339  --       0.261  0.847  1.601                                                                               0.87   3.55 --                                340  --       0.544  1.096  0.207                                                                               2.89   4.68 --                                ______________________________________                                    

                  TABLE 12-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         311   0.0076  0.003    0.018                                                                               5       169    47                                  312   0.0083  0.006    0.003                                                                               2       149    26                                  313   0.0161  0.003    0.009                                                                               5       141    18                                  314   0.0256  0.003    0.014                                                                               2       171    24                                  315   0.0026  0.003    0.015                                                                               1       168    14                                  316   0.0016  0.003    0.008                                                                               7       159    10                                  317   0.0027  0.004    0.019                                                                               6       172    12                                  318   0.0012  0.003    0.006                                                                               1       135    21                                  319   0.0218  0.005    0.005                                                                               2       151    24                                  320   0.0299  0.009    0.013                                                                               1       172    27                                  321   0.0206  0.001    0.007                                                                               6       175    30                                  322   0.0189  0.006    0.004                                                                               2       140    14                                  323   0.0199  0.009    0.009                                                                               4       168    33                                  324   0.0036  0.008    0.020                                                                               1       162    23                                  325   0.0100  0.002    0.014                                                                               1       151    16                                  326   0.0193  0.003    0.007                                                                               5       161    23                                  327   0.0266  0.010    0.016                                                                               6       170    18                                  328   0.0273  0.003    0.017                                                                               2       156    32                                  329   0.0012  0.003    0.019                                                                               3       148    40                                  330   0.0180  0.008    0.007                                                                               6       147    23                                  331   0.0281  0.009    0.007                                                                               6       156    35                                  332   0.0264  0.003    0.016                                                                               6       153    36                                  333   0.0086  0.008    0.013                                                                               6       166    16                                  334   0.0139  0.003    0.002                                                                               2       148    21                                  335   0.0224  0.006    0.011                                                                               6       151    31                                  336   0.0149  0.005    0.006                                                                               3       153    28                                  337   0.0166  0.008    0.005                                                                               6       132    24                                  338   0.0220  0.006    0.003                                                                               6       166    38                                  339   0.0262  0.004    0.018                                                                               0       131    33                                  340   0.0095  0.007    0.016                                                                               7       157    27                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 13-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         341  0.04   0.08   0.54 5.41 0.168                                                                               3.33 0.89 0.19 0.17                          342  0.30   0.77   0.60 8.00 0.184                                                                               2.60 0.64 0.02 0.22                          343  0.16   0.13   0.23 12.67                                                                               0.053                                                                               2.00 0.10 0.28 0.18                          344  0.14   0.37   0.92 17.37                                                                               0.596                                                                               0.93 0.11 0.41 0.24                          345  0.21   0.59   0.94 6.88 0.665                                                                               2.20 0.49 0.34 0.11                          346  0.03   0.66   0.54 5.17 0.092                                                                               0.30 0.11 0.22 0.01                          347  0.26   0.44   0.40 10.05                                                                               0.206                                                                               2.93 0.28 0.46 0.01                          348  0.30   0.60   0.39 6.34 0.342                                                                               2.94 0.34 0.49 0.20                          349  0.07   0.22   0.38 18.00                                                                               0.346                                                                               3.10 0.63 0.48 0.16                          350  0.13   0.34   0.63 16.75                                                                               0.539                                                                               2.88 0.98 0.10 0.11                          351  0.13   0.06   0.61 7.17 0.277                                                                               3.38 0.26 0.01 0.25                          352  0.03   0.04   0.20 6.57 0.387                                                                               2.43 0.76 0.13 0.17                          353  0.20   0.53   0.46 6.21 0.201                                                                               1.10 0.83 0.13 0.20                          354  0.18   0.62   0.86 17.01                                                                               0.057                                                                               2.16 0.81 0.42 0.17                          355  0.05   0.18   0.47 10.84                                                                               0.782                                                                               3.42 0.54 0.42 0.05                          356  0.06   0.64   0.35 11.51                                                                               0.730                                                                               2.69 0.85 0.07 0.03                          357  0.17   0.33   0.79 10.50                                                                               0.230                                                                               2.75 0.58 0.01 0.09                          358  0.02   0.28   0.43 5.52 0.600                                                                               2.99 0.05 0.16 0.05                          359  0.02   0.35   0.34 7.34 0.681                                                                               2.89 0.10 0.44 0.12                          360  0.11   0.43   0.42 14.27                                                                               0.844                                                                               2.01 0.59 0.30 0.02                          361  0.25   0.40   0.53 11.04                                                                               0.407                                                                               3.04 0.36 0.13 0.20                          362  0.09   0.12   0.52 14.75                                                                               0.187                                                                               2.10 0.21 0.09 0.12                          363  0.18   0.62   0.27 10.49                                                                               0.036                                                                               2.00 0.97 0.10 0.12                          364  0.03   0.23   0.85 9.05 0.284                                                                               2.18 0.04 0.10 0.15                          365  0.16   0.38   0.53 8.42 0.777                                                                               2.12 0.20 0.49 0.06                          366  0.11   0.54   0.37 12.80                                                                               0.344                                                                               2.88 0.79 0.44 0.03                          367  0.25   0.60   0.64 7.02 0.311                                                                               0.65 0.66 0.37 0.04                          368  0.25   0.02   0.42 15.15                                                                               0.529                                                                               1.50 0.16 0.21 0.17                          369  0.21   0.25   0.77 15.44                                                                               0.331                                                                               3.23 0.10 0.11 0.13                          370  0.07   0.77   0.76 12.22                                                                               0.544                                                                               0.32 0.31 0.23 0.13                          ______________________________________                                    

                  TABLE 13-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         341  --       0.887  1.780  1.610                                                                               0.52   2.29 --                                342  --       0.994  0.592  1.507                                                                               2.62   0.45 --                                343  0.348    --     0.174  1.543                                                                               1.10   0.69 --                                344  1.622    --     0.191  0.385                                                                               4.84   2.25 --                                345  1.781    --     1.336  1.719                                                                               1.03   1.95 --                                346  1.478    --     0.290  0.230                                                                               0.91   3.83 --                                347  0.402    --     1.705  1.569                                                                               1.28   2.27 --                                348  0.205    --     1.264  1.418                                                                               1.34   1.28 --                                349  1.566    1.846  --     1.445                                                                               0.31   4.89 --                                350  0.166    0.064  --     1.322                                                                               2.21   2.70 --                                351  1.679    1.062  --     1.712                                                                               1.41   1.11 --                                352  0.775    0.508  --     1.290                                                                               4.35   1.72 --                                353  1.108    1.097  --     1.754                                                                               0.70   3.83 --                                354  0.365    0.493  --     1.750                                                                               1.60   4.18 --                                355  0.197    0.371  0.494  1.962                                                                               3.91   4.41 --                                356  0.307    1.385  0.353  1.051                                                                               4.39   1.30 --                                357  0.354    0.230  0.404  1.689                                                                               2.27   3.65 --                                358  1.966    1.537  1.288  0.549                                                                               1.58   1.13 --                                359  0.872    1.011  1.703  1.293                                                                               1.49   4.89 --                                360  0.766    1.341  1.345  0.632                                                                               3.70   4.63 --                                361  1.274    --     --     --   --     --   0.78                              362  0.074    --     --     --   --     --   1.77                              363  1.826    --     --     --   --     --   1.57                              364  1.239    --     --     --   --     --   0.80                              365  0.962    --     --     --   --     --   0.95                              366  0.660    --     --     --   --     --   1.73                              367  --       1.386  --     --   --     --   1.95                              368  --       0.581  --     --   --     --   1.32                              369  --       0.640  --     --   --     --   1.31                              370  --       0.253  --     --   --     --   0.76                              ______________________________________                                    

                  TABLE 13-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         341   0.0268  0.009    0.015                                                                               4       170    44                                  342   0.0284  0.003    0.020                                                                               2       149    37                                  343   0.0094  0.005    0.019                                                                               6       146    30                                  344   0.0242  0.006    0.008                                                                               7       138    26                                  345   0.0236  0.005    0.014                                                                               5       180    51                                  346   0.0028  0.007    0.014                                                                               6       148    20                                  347   0.0164  0.004    0.004                                                                               1       169    40                                  348   0.0144  0.002    0.002                                                                               4       173    27                                  349   0.0075  0.005    0.002                                                                               5       161    43                                  350   0.0200  0.002    0.013                                                                               1       161    26                                  351   0.0026  0.009    0.003                                                                               5       177    40                                  352   0.0098  0.003    0.005                                                                               4       136    26                                  353   0.0222  0.005    0.008                                                                               5       164    42                                  354   0.0199  0.004    0.019                                                                               2       166    26                                  355   0.0128  0.008    0.004                                                                               2       170    30                                  356   0.0109  0.006    0.010                                                                               4       176    32                                  357   0.0239  0.005    0.003                                                                               6       165    26                                  358   0.0029  0.005    0.011                                                                               5       162    46                                  359   0.0019  0.004    0.009                                                                               0       146    50                                  360   0.0018  0.004    0.006                                                                               0       146    45                                  361   0.0121  0.010    0.016                                                                               3       137    24                                  362   0.0282  0.005    0.008                                                                               5       173     9                                  363   0.0151  0.002    0.008                                                                               6       133    26                                  364   0.0279  0.004    0.012                                                                               4       168    20                                  365   0.0018  0.010    0.008                                                                               3       156    18                                  366   0.0213  0.008    0.002                                                                               3       175    13                                  367   0.0223  0.002    0.020                                                                               6       153    22                                  368   0.0293  0.005    0.020                                                                               0       168    17                                  369   0.0077  0.009    0.018                                                                               6       146    16                                  370   0.0122  0.005    0.011                                                                               3       167    11                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 14-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         371  0.08   0.27   0.26 16.45                                                                               0.018                                                                               2.17 0.65 0.02 0.01                          372  0.20   0.20   0.73 6.46 0.575                                                                               3.27 0.94 0.12 0.09                          373  0.08   0.02   0.45 6.10 0.063                                                                               3.07 0.05 0.46 0.08                          374  0.12   0.79   0.49 6.75 0.806                                                                               2.70 0.26 0.21 0.07                          375  0.11   0.43   0.71 12.68                                                                               0.144                                                                               3.22 0.92 0.03 0.02                          376  0.02   0.76   0.58 8.94 0.916                                                                               0.85 0.91 0.34 0.25                          377  0.23   0.07   0.78 12.81                                                                               0.463                                                                               3.28 0.53 0.31 0.12                          378  0.25   0.22   0.37 9.20 0.114                                                                               1.71 0.13 0.12 0.20                          379  0.19   0.28   0.41 8.84 0.204                                                                               0.54 0.03 0.41 0.07                          380  0.15   0.13   0.38 16.29                                                                               0.071                                                                               0.58 0.07 0.36 0.07                          381  0.21   0.80   0.54 16.16                                                                               0.047                                                                               2.22 0.09 0.41 0.03                          382  0.19   0.22   0.77 12.97                                                                               0.962                                                                               0.66 0.42 0.44 0.15                          383  0.03   0.21   0.94 17.69                                                                               0.675                                                                               0.67 0.40 0.16 0.16                          384  0.28   0.65   0.50 8.60 0.509                                                                               3.34 0.38 0.20 0.14                          385  0.02   0.63   0.55 16.04                                                                               0.796                                                                               3.15 0.18 0.25 0.04                          386  0.20   0.41   0.53 5.40 0.872                                                                               2.90 0.63 0.46 0.06                          387  0.07   0.24   0.31 6.94 0.081                                                                               2.01 0.58 0.03 0.18                          388  0.15   0.40   0.57 5.67 0.747                                                                               1.62 0.86 0.34 0.10                          389  0.24   0.75   0.79 5.97 0.219                                                                               2.81 0.81 0.33 0.14                          390  0.02   0.39   0.81 5.60 0.327                                                                               3.43 0.28 0.16 0.04                          391  0.15   0.74   0.92 15.52                                                                               0.905                                                                               1.25 0.08 0.01 0.23                          392  0.02   0.52   0.58 7.52 0.787                                                                               2.33 0.04 0.28 0.19                          393  0.15   0.75   0.87 5.49 0.322                                                                               1.19 1.00 0.40 0.11                          394  0.21   0.15   0.83 13.76                                                                               0.326                                                                               0.60 0.34 0.04 0.10                          395  0.29   0.55   0.77 10.90                                                                               0.159                                                                               3.33 0.84 0.11 0.09                          396  0.20   0.23   0.53 7.47 0.628                                                                               2.16 0.37 0.03 0.05                          397  0.04   0.27   0.79 8.05 0.094                                                                               1.60 0.75 0.22 0.19                          398  0.20   0.12   0.21 16.99                                                                               0.876                                                                               1.04 0.82 0.35 0.22                          399  0.19   0.05   0.66 12.52                                                                               0.822                                                                               3.27 0.91 0.33 0.22                          400  0.11   0.73   0.82 5.70 0.768                                                                               2.80 0.88 0.33 0.05                          ______________________________________                                    

                  TABLE 14-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         371  --       0.091  --     --   --     --   0.28                              372  --       0.838  --     --   --     --   1.35                              373  1.534    1.141  --     --   --     --   0.98                              374  1.298    0.693  --     --   --     --   0.69                              375  1.068    0.158  --     --   --     --   1.96                              376  1.546    0.191  --     --   --     --   0.91                              377  0.417    1.485  --     --   --     --   1.75                              378  1.320    1.709  --     --   --     --   0.58                              379  --       --     1.218  --   --     --   0.70                              380  --       --     0.977  --   --     --   0.92                              381  --       --     0.050  --   --     --   0.94                              382  --       --     1.100  --   --     --   0.46                              383  --       --     0.792  --   --     --   0.99                              384  --       --     1.824  --   --     --   1.34                              385  0.337    --     1.856  --   --     --   0.31                              386  0.783    --     0.562  --   --     --   1.20                              387  0.325    --     1.566  --   --     --   1.01                              388  0.636    --     0.619  --   --     --   0.37                              389  1.374    --     1.370  --   --     --   1.68                              390  1.231    --     0.468  --   --     --   1.01                              391  --       1.846  0.600  --   --     --   1.71                              392  --       0.615  0.427  --   --     --   0.75                              393  --       0.388  0.627  --   --     --   0.56                              394  --       0.845  1.877  --   --     --   1.72                              395  --       1.652  0.850  --   --     --   0.36                              396  --       0.485  1.208  --   --     --   1.57                              397  1.632    1.997  0.622  --   --     --   1.45                              398  1.522    1.895  1.780  --   --     --   1.51                              399  1.575    0.817  1.332  --   --     --   1.47                              400  0.458    0.455  1.965  --   --     --   1.02                              ______________________________________                                    

                  TABLE 14-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         371   0.0084  0.009    0.016                                                                               3       158    12                                  372   0.0210  0.002    0.019                                                                               7       146    20                                  373   0.0002  0.004    0.017                                                                               3       159    31                                  374   0.0011  0.006    0.017                                                                               5       175    24                                  375   0.0184  0.009    0.005                                                                               1       172    23                                  376   0.0028  0.005    0.009                                                                               3       177    28                                  377   0.0239  0.004    0.005                                                                               0       143    23                                  378   0.0024  0.005    0.009                                                                               5       149    29                                  379   0.0226  0.007    0.008                                                                               3       146    21                                  380   0.0200  0.009    0.010                                                                               6       162    19                                  381   0.0048  0.003    0.020                                                                               3       175    11                                  382   0.0167  0.003    0.006                                                                               3       163    19                                  383   0.0058  0.003    0.014                                                                               2       153    12                                  384   0.0274  0.009    0.002                                                                               6       149    21                                  385   0.0167  0.003    0.005                                                                               5       178    28                                  386   0.0132  0.009    0.009                                                                               3       167    22                                  387   0.0125  0.009    0.014                                                                               2       145    25                                  388   0.0247  0.001    0.004                                                                               5       165    23                                  389   0.0299  0.002    0.017                                                                               3       153    31                                  390   0.0227  0.009    0.019                                                                               5       138    19                                  391   0.0138  0.004    0.017                                                                               7       147    31                                  392   0.0276  0.008    0.008                                                                               1       158    13                                  393   0.0149  0.005    0.008                                                                               6       150    21                                  394   0.0152  0.008    0.014                                                                               1       173    34                                  395   0.0091  0.006    0.014                                                                               2       158    30                                  396   0.0210  0.007    0.003                                                                               7       180    24                                  397   0.0016  0.009    0.008                                                                               5       168    42                                  398   0.0056  0.001    0.006                                                                               6       175    47                                  399   0.0133  0.001    0.014                                                                               4       178    38                                  400   0.0046  0.002    0.018                                                                               2       155    29                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 15-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         401  0.20   0.06   0.54 13.75                                                                               0.541                                                                               2.37 0.55 0.28 0.24                          402  0.13   0.27   0.52 8.69 0.489                                                                               1.47 0.25 0.10 0.06                          403  0.28   0.43   1.00 14.23                                                                               0.934                                                                               2.83 0.32 0.42 0.17                          404  0.17   0.44   0.65 15.29                                                                               0.219                                                                               0.94 0.09 0.20 0.18                          405  0.19   0.54   0.56 16.25                                                                               0.678                                                                               0.26 0.89 0.34 0.16                          406  0.15   0.21   0.57 8.35 0.646                                                                               1.85 0.10 0.27 0.21                          407  0.14   0.51   0.57 9.18 0.465                                                                               0.25 0.99 0.14 0.03                          408  0.11   0.52   0.82 16.50                                                                               0.964                                                                               3.17 0.46 0.13 0.08                          409  0.02   0.12   0.80 15.18                                                                               0.984                                                                               3.45 0.30 0.39 0.18                          410  0.25   0.73   0.75 9.38 0.845                                                                               2.16 0.85 0.37 0.07                          411  0.19   0.67   0.98 16.87                                                                               0.910                                                                               0.50 0.48 0.46 0.06                          412  0.20   0.59   0.53 15.88                                                                               0.010                                                                               2.85 0.99 0.10 0.23                          413  0.26   0.76   0.48 17.11                                                                               0.459                                                                               2.03 0.74 0.19 0.19                          414  0.01   0.66   0.29 12.13                                                                               0.611                                                                               0.83 0.07 0.16 0.25                          415  0.14   0.53   0.24 5.06 0.293                                                                               0.33 0.76 0.17 0.13                          416  0.02   0.27   0.98 13.47                                                                               0.848                                                                               1.67 0.22 0.38 0.16                          417  0.18   0.52   0.80 15.67                                                                               0.112                                                                               2.64 0.24 0.47 0.17                          418  0.29   0.37   0.36 16.09                                                                               0.914                                                                               2.72 0.67 0.37 0.01                          419  0.15   0.09   0.73 12.59                                                                               0.107                                                                               1.37 0.36 0.48 0.12                          420  0.29   0.33   0.98 15.88                                                                               0.997                                                                               1.30 0.61 0.23 0.09                          421  0.24   0.57   0.57 17.53                                                                               0.946                                                                               2.01 0.29 0.02 0.02                          422  0.08   0.67   0.58 15.17                                                                               0.280                                                                               1.30 0.23 0.03 0.21                          423  0.21   0.13   0.47 13.45                                                                               0.340                                                                               1.95 0.25 0.18 0.15                          424  0.14   0.38   0.51 16.45                                                                               0.446                                                                               3.35 0.19 0.37 0.04                          425  0.12   0.50   0.57 9.23 0.450                                                                               1.73 0.88 0.05 0.09                          426  0.10   0.76   0.53 15.66                                                                               0.189                                                                               3.11 0.69 0.11 0.12                          427  0.17   0.25   0.64 14.01                                                                               0.981                                                                               0.37 0.42 0.47 0.10                          428  0.15   0.41   0.38 15.19                                                                               0.190                                                                               1.23 0.92 0.32 0.24                          429  0.27   0.32   0.42 10.62                                                                               0.630                                                                               1.82 0.53 0.31 0.13                          430  0.06   0.65   0.22 11.12                                                                               0.646                                                                               3.26 0.58 0.12 0.10                          ______________________________________                                    

                  TABLE 15-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         401  0.848    1.455  1.334  --   --     --   0.74                              402  1.406    0.521  1.130  --   --     --   0.37                              403  --       --     --     0.647                                                                               --     --   1.41                              404  --       --     --     1.144                                                                               --     --   1.76                              405  --       --     --     0.462                                                                               --     --   0.23                              406  --       --     --     0.253                                                                               --     --   1.01                              407  --       --     --     1.189                                                                               --     --   1.12                              408  --       --     --     1.944                                                                               --     --   0.25                              409  0.479    --     --     0.181                                                                               --     --   0.82                              410  0.577    --     --     1.580                                                                               --     --   0.72                              411  1.898    --     --     0.818                                                                               --     --   1.47                              412  1.113    --     --     1.575                                                                               --     --   1.88                              413  1.885    --     --     1.512                                                                               --     --   0.73                              414  1.885    --     --     0.287                                                                               --     --   0.43                              415  --       0.946  --     0.587                                                                               --     --   1.60                              416  --       1.300  --     1.065                                                                               --     --   1.22                              417  --       0.795  --     0.427                                                                               --     --   0.82                              418  --       1.075  --     0.310                                                                               --     --   1.90                              419  --       0.840  --     1.414                                                                               --     --   1.46                              420  --       1.756  --     0.398                                                                               --     --   1.89                              421  --       --     1.768  1.928                                                                               --     --   0.22                              422  --       --     1.066  1.688                                                                               --     --   0.64                              423  --       --     1.890  1.344                                                                               --     --   1.95                              424  --       --     1.902  0.556                                                                               --     --   0.27                              425  --       --     0.821  1.035                                                                               --     --   0.71                              426  --       --     0.277  1.420                                                                               --     --   0.25                              427  --       1.683  1.936  1.383                                                                               --     --   1.31                              428  --       0.951  0.485  1.593                                                                               --     --   0.90                              429  --       1.417  0.591  1.732                                                                               --     --   1.40                              430  --       0.760  1.950  0.497                                                                               --     --   1.66                              ______________________________________                                    

                  TABLE 15-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         401   0.0047  0.003    0.006                                                                               7       134    45                                  402   0.0234  0.007    0.014                                                                               5       142    38                                  403   0.0112  0.003    0.008                                                                               4       132    16                                  404   0.0230  0.003    0.015                                                                               1       133    17                                  405   0.0238  0.002    0.013                                                                               4       146    18                                  406   0.0240  0.002    0.007                                                                               3       149    11                                  407   0.0035  0.002    0.005                                                                               1       171    16                                  408   0.0169  0.009    0.003                                                                               4       139    20                                  409   0.0151  0.005    0.008                                                                               4       130    18                                  410   0.0074  0.009    0.007                                                                               2       173    22                                  411   0.0195  0.008    0.016                                                                               2       145    26                                  412   0.0163  0.003    0.012                                                                               6       173    27                                  413   0.0078  0.008    0.003                                                                               2       136    40                                  414   0.0039  0.007    0.012                                                                               7       162    22                                  415   0.0149  0.002    0.010                                                                               1       177    26                                  416   0.0208  0.007    0.002                                                                               2       160    30                                  417   0.0018  0.002    0.005                                                                               0       139    14                                  418   0.0127  0.002    0.004                                                                               2       166    18                                  419   0.0190  0.003    0.018                                                                               4       169    22                                  420   0.0153  0.008    0.003                                                                               0       151    25                                  421   0.0121  0.004    0.015                                                                               4       139    42                                  422   0.0043  0.006    0.011                                                                               3       161    27                                  423   0.0018  0.002    0.009                                                                               4       146    36                                  424   0.0149  0.004    0.005                                                                               2       169    24                                  425   0.0240  0.003    0.014                                                                               3       161    26                                  426   0.0085  0.004    0.005                                                                               6       172    26                                  427   0.0089  0.003    0.004                                                                               2       131    52                                  428   0.0201  0.002    0.007                                                                               4       141    34                                  429   0.0222  0.005    0.002                                                                               5       179    37                                  430   0.0257  0.005    0.014                                                                               6       173    32                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 16-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         431  0.19   0.08   0.86 8.06 0.572                                                                               3.36 0.41 0.15 0.10                          432  0.03   0.05   0.59 12.20                                                                               0.236                                                                               1.55 0.84 0.09 0.22                          433  0.26   0.44   0.51 8.61 0.483                                                                               2.27 0.72 0.33 0.05                          434  0.11   0.72   0.85 14.45                                                                               0.648                                                                               1.68 0.40 0.31 0.03                          435  0.11   0.38   0.71 8.35 0.574                                                                               2.56 0.70 0.20 0.14                          436  0.21   0.436  0.75 7.52 0.092                                                                               1.03 0.45 0.15 0.20                          437  0.22   0.44   0.43 16.23                                                                               0.519                                                                               3.12 0.97 0.34 0.18                          438  0.24   0.58   0.82 12.89                                                                               0.711                                                                               1.74 0.65 0.43 0.04                          439  0.08   0.38   0.60 8.48 0.502                                                                               1.28 0.28 0.35 0.10                          440  0.26   0.46   0.44 7.36 0.227                                                                               2.87 0.70 0.02 0.08                          441  0.16   0.72   0.99 13.74                                                                               0.713                                                                               1.00 0.28 0.09 0.06                          442  0.03   0.63   0.53 6.15 0.813                                                                               3.39 0.81 0.24 0.24                          443  0.10   0.46   0.54 8.40 0.850                                                                               2.87 0.17 0.13 0.10                          444  0.04   0.46   0.86 11.81                                                                               0.661                                                                               2.22 0.16 0.44 0.09                          445  0.23   0.50   0.99 14.35                                                                               0.090                                                                               0.90 0.62 0.33 0.15                          446  0.04   0.08   0.78 13.83                                                                               0.463                                                                               1.66 0.40 0.46 0.03                          447  0.17   0.23   0.90 14.57                                                                               0.618                                                                               2.32 0.82 0.27 0.02                          448  0.26   0.05   0.83 8.08 0.402                                                                               0.70 0.27 0.17 0.23                          449  0.27   0.57   0.83 11.65                                                                               0.143                                                                               1.18 1.00 0.31 0.23                          450  0.29   0.50   0.77 16.57                                                                               0.669                                                                               1.59 0.42 0.38 0.25                          451  0.29   0.10   0.52 7.82 0.828                                                                               1.38 0.82 0.29 0.23                          452  0.21   0.03   0.34 15.62                                                                               0.446                                                                               1.63 0.56 0.21 0.14                          453  0.29   0.54   0.52 5.58 0.371                                                                               1.86 0.46 0.30 0.06                          454  0.05   0.72   0.90 14.33                                                                               0.928                                                                               3.14 0.86 0.48 0.06                          455  0.18   0.45   0.57 13.87                                                                               0.463                                                                               3.28 0.12 0.19 0.24                          456  0.17   0.39   0.60 15.03                                                                               0.303                                                                               3.39 0.54 0.31 0.19                          457  0.15   0.79   0.84 9.06 0.777                                                                               1.26 0.46 0.28 0.22                          458  0.19   0.34   0.37 7.00 0.239                                                                               2.98 0.24 0.27 0.07                          459  0.26   0.11   0.27 6.71 0.517                                                                               1.40 0.70 0.19 0.05                          460  0.30   0.74   0.79 12.50                                                                               0.448                                                                               0.94 0.68 0.22 0.24                          ______________________________________                                    

                  TABLE 16-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         431  --       0.639  1.211  0.524                                                                               --     --   1.34                              432  --       0.726  0.049  0.494                                                                               --     --   1.06                              433  0.765    --     1.131  1.079                                                                               --     --   0.54                              434  1.520    --     1.120  0.937                                                                               --     --   1.25                              435  1.628    --     1.707  0.763                                                                               --     --   0.21                              436  1.741    --     0.571  0.229                                                                               --     --   0.75                              437  0.521    --     0.369  0.994                                                                               --     --   1.65                              438  0.678    --     1.778  0.745                                                                               --     --   1.73                              439  1.855    1.633  --     0.136                                                                               --     --   1.57                              440  1.728    1.576  --     0.842                                                                               --     --   1.78                              441  0.993    1.759  --     0.519                                                                               --     --   1.17                              442  0.294    1.893  --     1.869                                                                               --     --   1.25                              443  0.312    1.621  --     0.568                                                                               --     --   1.72                              444  0.709    0.615  --     0.247                                                                               --     --   1.40                              445  0.170    1.548  1.008  1.616                                                                               --     --   0.86                              446  1.375    1.100  0.448  1.332                                                                               --     --   0.75                              447  1.970    1.952  0.558  0.087                                                                               --     --   1.64                              448  0.671    1.758  1.983  1.521                                                                               --     --   1.45                              449  0.094    0.199  1.411  1.326                                                                               --     --   0.77                              450  0.950    1.927  0.503  0.154                                                                               --     --   0.22                              451  0.901    --     --     --   4.33   --   0.42                              452  0.608    --     --     --   2.63   --   1.03                              453  0.758    --     --     --   1.95   --   0.89                              454  0.010    --     --     --   3.93   --   1.50                              455  1.046    --     --     --   0.49   --   0.74                              456  1.534    --     --     --   0.53   --   1.06                              457  --       0.062  --     --   0.83   --   0.33                              458  --       1.419  --     --   3.00   --   1.86                              459  --       1.131  --     --   3.86   --   0.85                              460  --       1.846  --     --   4.98   --   1.52                              ______________________________________                                    

                  TABLE 16-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         431   0.0101  0.006    0.012                                                                               0       176    32                                  432   0.0157  0.006    0.001                                                                               3       166    22                                  433   0.0226  0.003    0.008                                                                               2       144    32                                  434   0.0108  0.005    0.020                                                                               2       140    37                                  435   0.0053  0.002    0.014                                                                               3       131    40                                  436   0.0165  0.006    0.006                                                                               4       144    33                                  437   0.0242  0.010    0.013                                                                               6       132    23                                  438   0.0088  0.009    0.012                                                                               2       172    38                                  439   0.0099  0.005    0.009                                                                               3       169    33                                  440   0.0078  0.002    0.002                                                                               6       149    36                                  441   0.0124  0.003    0.007                                                                               5       141    31                                  442   0.0190  0.006    0.010                                                                               1       171    36                                  443   0.0226  0.001    0.017                                                                               3       167    28                                  444   0.0036  0.009    0.009                                                                               1       159    23                                  445   0.0015  0.010    0.008                                                                               6       172    41                                  446   0.0268  0.002    0.013                                                                               4       135    37                                  447   0.0146  0.004    0.010                                                                               1       150    47                                  448   0.0197  0.007    0.006                                                                               6       170    52                                  449   0.0074  0.007    0.017                                                                               3       174    31                                  450   0.0176  0.006    0.003                                                                               6       138    33                                  451   0.0007  0.008    0.006                                                                               3       141    15                                  452   0.0114  0.002    0.005                                                                               0       135    18                                  453   0.0149  0.009    0.016                                                                               3       173    13                                  454   0.0214  0.009    0.017                                                                               3       133    11                                  455   0.0107  0.002    0.005                                                                               3       142    18                                  456   0.0084  0.007    0.005                                                                               5       178    26                                  457   0.0091  0.002    0.004                                                                               5       144    11                                  458   0.0229  0.002    0.010                                                                               5       143    24                                  459   0.0152  0.002    0.008                                                                               7       152    16                                  460   0.0107  0.004    0.006                                                                               3       149    25                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 17-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         461  0.27   0.54   0.21 15.79                                                                               0.868                                                                               2.70 0.03 0.01 0.01                          462  0.13   0.55   0.80 7.85 0.113                                                                               1.18 0.06 0.24 0.15                          463  0.25   0.26   0.41 6.09 0.014                                                                               0.77 0.11 0.07 0.03                          464  0.30   0.30   0.93 14.73                                                                               0.397                                                                               2.59 0.51 0.18 0.19                          465  0.23   0.57   0.62 12.45                                                                               0.620                                                                               2.82 0.12 0.47 0.14                          466  0.14   0.54   0.55 9.95 0.021                                                                               2.57 0.27 0.13 0.18                          467  0.28   0.09   0.59 11.56                                                                               0.409                                                                               2.93 0.28 0.31 0.16                          468  0.01   0.24   0.60 15.14                                                                               0.641                                                                               3.35 0.99 0.43 0.03                          469  0.02   0.49   0.46 5.65 0.550                                                                               1.67 0.27 0.18 0.25                          470  0.25   0.72   0.44 13.48                                                                               0.473                                                                               0.64 0.90 0.20 0.04                          471  0.08   0.78   0.80 16.87                                                                               0.738                                                                               1.34 0.26 0.17 0.21                          472  0.18   0.56   0.61 13.71                                                                               0.186                                                                               3.25 0.66 0.26 0.24                          473  0.22   0.70   0.94 14.90                                                                               0.146                                                                               0.85 0.45 0.37 0.10                          474  0.29   0.68   0.86 5.26 0.960                                                                               1.91 0.94 0.44 0.21                          475  0.06   0.38   0.23 15.27                                                                               0.969                                                                               2.54 0.04 0.39 0.19                          476  0.21   0.47   0.55 10.34                                                                               0.013                                                                               0.58 0.98 0.13 0.11                          477  0.25   0.40   0.86 14.23                                                                               0.918                                                                               0.44 0.69 0.07 0.05                          478  0.13   0.05   0.62 11.72                                                                               0.517                                                                               3.18 0.94 0.14 0.10                          479  0.11   0.48   0.53 7.37 0.157                                                                               1.72 0.13 0.49 0.21                          480  0.26   0.38   0.84 5.44 0.166                                                                               0.43 0.52 0.07 0.11                          481  0.12   0.79   0.22 10.31                                                                               0.878                                                                               0.43 0.50 0.26 0.11                          482  0.07   0.41   0.55 13.34                                                                               0.637                                                                               2.82 0.39 0.26 0.18                          483  0.20   0.28   0.47 5.80 0.764                                                                               2.09 0.51 0.22 0.03                          484  0.04   0.29   0.28 11.76                                                                               0.117                                                                               1.05 0.72 0.06 0.24                          485  0.12   0.28   0.63 15.93                                                                               0.014                                                                               2.40 0.84 0.20 0.15                          486  0.09   0.55   0.60 9.73 0.294                                                                               0.71 0.23 0.31 0.09                          487  0.06   0.55   0.85 10.58                                                                               0.799                                                                               0.36 0.21 0.06 0.14                          488  0.27   0.57   0.85 9.79 0.363                                                                               0.78 0.58 0.10 0.02                          489  0.23   0.06   0.87 11.59                                                                               0.812                                                                               1.47 0.74 0.12 0.17                          490  0.05   0.09   0.39 7.64 0.499                                                                               0.22 0.49 0.04 0.07                          ______________________________________                                    

                  TABLE 17-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         461  --       0.284  --     --   0.84   --   0.86                              462  --       0.053  --     --   2.56   --   0.37                              463  1.029    0.881  --     --   2.58   --   1.59                              464  0.305    0.413  --     --   3.94   --   1.50                              465  0.086    1.331  --     --   1.93   --   0.68                              466  1.035    0.284  --     --   0.30   --   1.57                              467  1.834    1.978  --     --   0.66   --   0.27                              468  1.127    0.071  --     --   2.23   --   1.89                              469  --       --     1.350  --   1.78   --   1.60                              470  --       --     1.931  --   0.92   --   1.83                              471  --       --     0.305  --   3.74   --   0.51                              472  --       --     1.140  --   2.19   --   0.89                              473  --       --     1.093  --   2.73   --   1.83                              474  --       --     0.834  --   4.53   --   1.19                              475  1.094    --     0.052  --   1.99   --   0.49                              476  1.700    --     1.388  --   3.94   --   0.33                              477  0.871    --     1.545  --   2.39   --   0.43                              478  0.274    --     1.194  --   3.81   --   0.50                              479  0.595    --     1.995  --   4.95   --   0.23                              480  0.478    --     0.636  --   2.62   --   0.21                              481  --       1.988  1.762  --   0.90   --   1.08                              482  -        1.189  0.072  --   3.74   --   1.62                              483  --       0.864  0.220  --   0.76   --   0.65                              484  --       1.683  0.881  --   3.17   --   1.45                              485  --       0.327  0.723  --   2.97   --   1.04                              486  --       0.457  1.435  --   1.82   --   1.83                              487  0.262    1.739  1.663  --   3.70   --   1.72                              488  0.936    0.868  0.105  --   3.02   --   0.41                              489  1.241    0.503  0.415  --   1.41   --   0.31                              490  0.844    1.313  1.270  --   0.44   --   0.22                              ______________________________________                                    

                  TABLE 17-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         461   0.0195  0.003    0.019                                                                               3       162     9                                  462   0.0220  0.002    0.007                                                                               1       144    13                                  463   0.0282  0.004    0.014                                                                               4       147    26                                  464   0.0182  0.007    0.017                                                                               1       149    12                                  465   0.0165  0.005    0.004                                                                               5       177    23                                  466   0.0189  0.001    0.001                                                                               3       161    19                                  467   0.0202  0.004    0.014                                                                               3       176    41                                  468   0.0008  0.001    0.010                                                                               5       151    17                                  469   0.0150  0.006    0.016                                                                               6       165    22                                  470   0.0282  0.004    0.019                                                                               6       143    28                                  471   0.0061  0.005    0.007                                                                               2       139    16                                  472   0.0182  0.006    0.014                                                                               3       132    23                                  473   0.0148  0.003    0.008                                                                               4       173    23                                  474   0.0206  0.009    0.006                                                                               4       141    17                                  475   0.0160  0.009    0.013                                                                               2       162    16                                  476   0.0260  0.002    0.018                                                                               4       166    34                                  477   0.0157  0.009    0.007                                                                               1       154    24                                  478   0.0105  0.009    0.016                                                                               3       154    21                                  479   0.0050  0.002    0.004                                                                               6       170    26                                  480   0.0243  0.009    0.014                                                                               4       178    20                                  481   0.0040  0.005    0.015                                                                               1       157    40                                  482   0.0286  0.008    0.005                                                                               5       158    21                                  483   0.0185  0.002    0.008                                                                               4       161    15                                  484   0.0136  0.003    0.011                                                                               2       168    32                                  485   0.0089  0.006    0.012                                                                               2       156    14                                  486   0.0147  0.005    0.008                                                                               4       153    25                                  487   0.0110  0.008    0.015                                                                               7       137    41                                  488   0.0228  0.003    0.009                                                                               3       136    23                                  489   0.0152  0.003    0.008                                                                               1       177    30                                  490   0.0283  0.002    0.008                                                                               5       164    38                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 18-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         491  0.11   0.52   0.86 8.60 0.255                                                                               3.11 0.18 0.26 0.04                          492  0.22   0.44   0.96 12.39                                                                               0.406                                                                               1.30 0.62 0.45 0.05                          493  0.18   0.12   0.55 10.29                                                                               0.285                                                                               2.52 0.68 0.29 0.05                          494  0.10   0.59   0.71 6.80 0.746                                                                               2.96 0.68 0.19 0.24                          495  0.06   0.18   0.91 12.91                                                                               0.623                                                                               2.06 0.46 0.32 0.23                          496  0.03   0.70   0.61 6.71 0.744                                                                               0.94 0.84 0.36 0.09                          497  0.11   0.46   0.87 12.13                                                                               0.441                                                                               0.67 0.19 0.45 0.03                          498  0.23   0.12   0.39 14.14                                                                               0.553                                                                               0.73 0.30 0.04 0.13                          499  0.21   0.32   0.99 16.95                                                                               0.917                                                                               0.58 0.53 0.26 0.10                          500  0.15   0.16   0.59 12.09                                                                               0.371                                                                               1.32 0.72 0.07 0.15                          501  0.15   0.30   0.63 16.91                                                                               0.259                                                                               0.80 0.22 0.36 0.24                          502  0.16   0.21   0.58 16.24                                                                               0.900                                                                               3.39 0.34 0.06 0.08                          503  0.12   0.16   0.33 14.50                                                                               0.146                                                                               0.29 0.41 0.32 0.25                          504  0.29   0.79   0.51 9.34 0.813                                                                               2.54 0.78 0.09 0.21                          505  0.18   0.03   0.63 5.44 0.262                                                                               2.99 0.32 0.02 0.06                          506  0.18   0.10   0.94 13.51                                                                               0.811                                                                               2.75 0.80 0.02 0.11                          507  0.09   0.48   0.90 11.93                                                                               0.804                                                                               2.91 0.60 0.01 0.21                          508  0.01   0.64   0.39 17.95                                                                               0.566                                                                               1.27 0.05 0.17 0.18                          509  0.05   0.45   0.88 16.71                                                                               0.448                                                                               2.28 0.46 0.40 0.12                          510  0.14   0.58   0.23 5.75 0.275                                                                               0.41 0.70 0.15 0.22                          511  0.11   0.50   0.72 15.75                                                                               0.393                                                                               1.77 0.11 0.07 0.08                          512  0.04   0.48   0.22 11.89                                                                               0.129                                                                               2.46 0.97 0.30 0.15                          513  0.18   0.77   0.98 11.56                                                                               0.319                                                                               0.32 0.19 0.06 0.03                          514  0.19   0.08   0.88 6.15 0.302                                                                               3.04 0.05 0.47 0.03                          515  0.03   0.62   0.98 12.92                                                                               0.405                                                                               1.82 0.88 0.23 0.24                          516  0.08   0.70   0.38 10.44                                                                               0.978                                                                               1.11 0.09 0.25 0.14                          517  0.29   0.58   0.91 9.47 0.854                                                                               0.35 0.43 0.44 0.17                          518  0.04   0.53   0.45 7.77 0.857                                                                               2.25 0.29 0.23 0.04                          519  0.29   0.42   0.48 16.33                                                                               0.833                                                                               3.04 0.97 0.02 0.08                          520  0.13   0.50   0.46 13.55                                                                               0.621                                                                               0.51 0.84 0.49 0.14                          ______________________________________                                    

                  TABLE 18-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         491  1.420    0.968  1.336  --   1.78   --   0.74                              492  1.612    0.146  0.286  --   4.58   --   1.59                              493  --       --     --     1.815                                                                               0.92   --   0.66                              494  --       --     --     0.475                                                                               1.99   --   0.36                              495  --       --     --     1.386                                                                               2.13   --   1.29                              496  --       --     --     0.238                                                                               3.04   --   1.37                              497  --       --     --     0.718                                                                               1.53   --   0.29                              498  --       --     --     1.476                                                                               1.57   --   1.37                              499  1.378    --     --     1.204                                                                               4.81   --   0.69                              500  1.877    --     --     1.555                                                                               0.83   --   0.68                              501  1.073    --     --     0.228                                                                               0.89   --   1.03                              502  0.634    --     --     0.848                                                                               1.70   --   1.45                              503  1.207    --     --     1.123                                                                               2.60   --   0.74                              504  0.492    --     --     0.742                                                                               2.77   --   0.42                              505  --       0.599  --     0.337                                                                               1.40   --   1.09                              506  --       1.634  --     0.592                                                                               4.87   --   0.64                              507  --       1.272  --     1.196                                                                               2.87   --   0.58                              508  --       1.182  --     0.802                                                                               4.15   --   1.53                              509  --       1.043  --     0.094                                                                               0.75   --   1.38                              510  --       1.511  --     1.722                                                                               3.86   --   1.63                              511  --       --     1.968  0.357                                                                               0.65   --   1.08                              512  --       --     1.807  0.712                                                                               4.83   --   1.25                              513  --       --     0.631  0.404                                                                               1.12   --   1.83                              514  --       --     1.130  1.153                                                                               0.84   --   1.65                              515  --       --     1.970  0.608                                                                               3.14   --   0.41                              516  --       --     0.844  0.450                                                                               2.44   --   0.48                              517  --       1.406  1.361  1.320                                                                               0.29   --   1.60                              518  --       1.987  0.280  1.939                                                                               3.22   --   0.77                              519  --       1.217  1.199  1.948                                                                               0.76   --   1.29                              520  --       0.797  1.829  1.029                                                                               4.15   --   1.04                              ______________________________________                                    

                  TABLE 18-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         491   0.0123  0.002    0.006                                                                               3       173    39                                  492   0.0071  0.003    0.008                                                                               7       157    21                                  493   0.0079  0.003    0.012                                                                               2       146    24                                  494   0.0245  0.006    0.004                                                                               5       165    15                                  495   0.0233  0.003    0.010                                                                               3       143    16                                  496   0.0113  0.005    0.008                                                                               0       157     8                                  497   0.0017  0.009    0.014                                                                               5       136    16                                  498   0.0032  0.008    0.005                                                                               2       156    25                                  499   0.0261  0.002    0.008                                                                               1       147    30                                  500   0.0208  0.003    0.009                                                                               4       135    38                                  501   0.0119  0.009    0.005                                                                               7       148    25                                  502   0.0095  0.009    0.003                                                                               4       164    19                                  503   0.0092  0.003    0.018                                                                               6       160    25                                  504   0.0205  0.002    0.020                                                                               4       165    18                                  505   0.0240  0.005    0.014                                                                               4       131    15                                  506   0.0143  0.010    0.016                                                                               5       136    26                                  507   0.0018  0.007    0.014                                                                               6       133    24                                  508   0.0262  0.007    0.013                                                                               1       149    25                                  509   0.0082  0.010    0.002                                                                               1       162    23                                  510   0.0021  0.004    0.006                                                                               1       150    38                                  511   0.0033  0.003    0.012                                                                               6       140    32                                  512   0.0220  0.004    0.017                                                                               1       136    30                                  513   0.0080  0.006    0.018                                                                               4       164    17                                  514   0.0020  0.002    0.002                                                                               5       153    23                                  515   0.0135  0.001    0.014                                                                               7       131    34                                  516   0.0224  0.001    0.003                                                                               1       175    22                                  517   0.0097  0.006    0.013                                                                               5       163    39                                  518   0.0295  0.003    0.013                                                                               3       148    41                                  519   0.0026  0.002    0.019                                                                               1       157    39                                  520   0.0285  0.005    0.008                                                                               1       143    41                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 19-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         521  0.09   0.67   0.26 16.70                                                                               0.548                                                                               2.34 0.72 0.07 0.04                          522  0.11   0.77   0.96 17.31                                                                               0.463                                                                               3.08 0.45 0.16 0.24                          523  0.17   0.31   0.41 13.03                                                                               0.187                                                                               2.15 0.85 0.42 0.09                          524  0.05   0.31   0.89 8.43 0.069                                                                               0.70 0.29 0.29 0.15                          525  0.15   0.26   0.27 14.18                                                                               0.923                                                                               3.06 0.07 0.18 0.02                          526  0.28   0.42   0.41 15.26                                                                               0.613                                                                               0.54 0.05 0.02 0.03                          527  0.24   0.67   0.78 16.12                                                                               0.466                                                                               2.46 0.05 0.44 0.25                          528  0.13   0.49   0.86 14.48                                                                               0.808                                                                               3.32 0.90 0.16 0.17                          529  0.20   0.53   0.92 14.76                                                                               0.484                                                                               0.91 0.47 0.30 0.22                          530  0.10   0.27   0.41 14.93                                                                               0.335                                                                               1.34 0.08 0.06 0.01                          531  0.22   0.75   0.81 12.70                                                                               0.682                                                                               0.72 0.05 0.10 0.10                          532  0.08   0.68   0.39 12.54                                                                               0.873                                                                               3.49 0.72 0.33 0.09                          533  0.08   0.31   0.22 5.73 0.240                                                                               0.83 0.44 0.17 0.17                          534  0.29   0.69   0.55 16.06                                                                               0.103                                                                               0.43 0.53 0.29 0.07                          535  0.25   0.13   0.87 9.12 0.824                                                                               1.81 0.83 0.12 0.11                          536  0.20   0.46   0.25 15.12                                                                               0.223                                                                               2.73 0.20 0.30 0.13                          537  0.08   0.36   0.94 12.48                                                                               0.146                                                                               1.04 0.93 0.03 0.21                          538  0.28   0.12   0.83 12.06                                                                               0.418                                                                               1.13 0.41 0.45 0.20                          539  0.04   0.77   0.98 11.84                                                                               0.884                                                                               2.45 0.43 0.25 0.16                          530  0.03   0.22   0.84 15.87                                                                               0.871                                                                               1.14 0.84 0.09 0.19                          541  0.06   0.31   0.71 15.93                                                                               0.728                                                                               1.65 0.98 0.13 0.24                          542  0.22   0.52   0.84 16.03                                                                               0.282                                                                               1.77 0.70 0.05 0.16                          543  0.18   0.32   0.31 7.84 0.873                                                                               0.98 0.33 0.25 0.14                          544  0.03   0.37   0.58 14.93                                                                               0.328                                                                               0.32 0.18 0.41 0.14                          545  0.01   0.15   0.32 9.32 0.984                                                                               2.62 0.10 0.22 0.01                          546  0.09   0.71   0.60 15.01                                                                               0.200                                                                               0.74 0.93 0.31 0.19                          547  0.07   0.74   0.49 16.69                                                                               0.784                                                                               0.70 0.02 0.37 0.15                          548  0.04   0.52   0.26 12.21                                                                               0.582                                                                               1.96 0.18 0.31 0.22                          549  0.24   0.67   0.57 12.50                                                                               0.928                                                                               0.69 0.75 0.06 0.12                          550  0.20   0.70   0.90 8.91 0.161                                                                               2.94 0.09 0.02 0.17                          ______________________________________                                    

                  TABLE 19-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         521  --       1.365  0.836  0.848                                                                               2.98   --   0.67                              522  --       1.611  0.870  0.066                                                                               3.68   --   0.75                              523  1.828    --     0.653  1.394                                                                               3.12   --   1.91                              524  0.234    --     1.815  1.474                                                                               0.44   --   1.14                              525  1.435    --     0.036  1.973                                                                               4.44   --   1.74                              526  0.149    --     0.984  1.575                                                                               4.77   --   1.64                              527  0.015    --     1.338  0.941                                                                               0.62   --   0.50                              528  0.706    --     1.753  0.750                                                                               0.81   --   1.65                              529  0.888    1.824  --     1.679                                                                               4.58   --   0.31                              530  1.249    0.694  --     0.401                                                                               1.52   --   0.67                              531  0.462    1.294  --     0.588                                                                               2.86   --   1.52                              532  0.187    1.268  --     1.879                                                                               2.94   --   1.69                              533  0.075    1.335  --     1.002                                                                               3.49   --   0.89                              534  0.827    0.153  --     0.607                                                                               1.28   --   0.60                              535  0.120    0.372  1.380  1.348                                                                               2.68   --   1.44                              536  0.595    0.675  0.614  0.903                                                                               2.09   --   1.29                              537  0.960    1.725  0.976  0.955                                                                               3.62   --   0.79                              538  1.869    0.194  0.113  1.146                                                                               1.54   --   0.51                              539  1.982    1.779  0.737  0.198                                                                               2.41   --   1.98                              530  2.000    0.144  1.500  1.749                                                                               2.97   --   1.31                              541  0.566    --     --     --   --     2.44 0.88                              542  0.386    --     --     --   --     4.35 1.31                              543  1.093    --     --     --   --     2.05 0.50                              544  1.369    --     --     --   --     2.00 0.86                              545  1.909    --     --     --   --     3.39 1.19                              546  1.372    --     --     --   --     3.02 1.18                              547  --       0.694  --     --   --     4.87 1.45                              548  --       1.400  --     --   --     3.45 0.82                              549  --       0.936  --     --   --     0.29 0.76                              550  --       0.968  --     --   --     1.88 1.02                              ______________________________________                                    

                  TABLE 19-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         521   0.0127  0.001    0.016                                                                               3       134    34                                  522   0.0249  0.008    0.001                                                                               4       157    26                                  523   0.0009  0.009    0.008                                                                               0       142    38                                  524   0.0100  0.009    0.015                                                                               1       163    36                                  525   0.0025  0.005    0.018                                                                               6       151    39                                  526   0.0036  0.006    0.005                                                                               2       158    31                                  527   0.0229  0.005    0.010                                                                               4       161    25                                  528   0.0112  0.005    0.013                                                                               1       138    35                                  529   0.0084  0.005    0.018                                                                               1       166    46                                  530   0.0243  0.003    0.014                                                                               3       175    30                                  531   0.0091  0.003    0.016                                                                               1       165    31                                  532   0.0029  0.002    0.002                                                                               1       165    37                                  533   0.0011  0.005    0.017                                                                               3       178    26                                  534   0.0282  0.004    0.010                                                                               1       131    19                                  535   0.0048  0.008    0.006                                                                               2       153    34                                  536   0.0004  0.005    0.012                                                                               4       170    34                                  537   0.0252  0.004    0.005                                                                               7       162    45                                  538   0.0297  0.004    0.002                                                                               1       154    38                                  539   0.0090  0.006    0.009                                                                               4       175    43                                  530   0.0178  0.005    0.003                                                                               4       154    54                                  541   0.0063  0.004    0.001                                                                               3       167    11                                  542   0.0146  0.006    0.009                                                                               3       142    16                                  543   0.0225  0.001    0.015                                                                               4       157    20                                  544   0.0106  0.005    0.014                                                                               3       140    20                                  545   0.0037  0.003    0.015                                                                               5       169    26                                  546   0.0266  0.003    0.013                                                                               6       146    25                                  547   0.0297  0.008    0.015                                                                               4       148    17                                  548   0.0233  0.002    0.017                                                                               6       180    21                                  549   0.0022  0.007    0.008                                                                               2       168    13                                  550   0.0067  0.008    0.003                                                                               4       165    21                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 20-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         551  0.16   0.47   0.70 5.73 0.609                                                                               1.57 0.50 0.36 0.21                          552  0.06   0.25   0.67 14.06                                                                               0.626                                                                               1.03 0.35 0.26 0.08                          553  0.01   0.68   0.65 12.02                                                                               0.032                                                                               0.72 0.45 0.13 0.21                          554  0.25   0.48   0.93 10.68                                                                               0.669                                                                               3.45 0.65 0.14 0.22                          555  0.15   0.67   0.56 7.65 0.862                                                                               2.01 0.29 0.46 0.07                          556  0.10   0.36   0.22 7.62 0.968                                                                               0.89 0.68 0.26 0.18                          557  0.19   0.59   0.98 8.28 0.317                                                                               2.81 0.21 0.45 0.05                          558  0.24   0.06   0.71 14.01                                                                               0.235                                                                               2.28 0.16 0.46 0.23                          559  0.05   0.58   0.86 16.07                                                                               0.052                                                                               2.00 0.37 0.43 0.21                          560  0.15   0.08   0.92 5.99 0.622                                                                               1.56 0.22 0.32 0.06                          561  0.21   0.39   0.35 14.08                                                                               0.772                                                                               0.31 0.99 0.03 0.11                          562  0.17   0.21   0.62 12.26                                                                               0.843                                                                               2.71 0.58 0.21 0.07                          563  0.15   0.18   0.40 11.34                                                                               0.171                                                                               1.60 0.28 0.29 0.03                          564  0.22   0.58   0.76 15.69                                                                               0.086                                                                               1.39 0.43 0.44 0.07                          565  0.06   0.10   0.77 16.73                                                                               0.427                                                                               3.20 0.87 0.34 0.15                          566  0.06   0.56   0.29 12.23                                                                               0.028                                                                               3.16 0.45 0.39 0.23                          567  0.30   0.28   0.40 6.64 0.228                                                                               2.42 0.48 0.02 0.14                          568  0.16   0.68   0.95 17.20                                                                               0.850                                                                               2.03 0.81 0.13 0.10                          569  0.04   0.48   0.63 15.87                                                                               0.745                                                                               1.48 0.29 0.15 0.17                          570  0.16   0.69   0.49 6.96 0.736                                                                               0.20 0.22 0.49 0.09                          571  0.06   0.05   0.41 14.39                                                                               0.179                                                                               2.68 0.47 0.10 0.17                          572  0.26   0.75   0.66 16.58                                                                               0.888                                                                               3.35 0.36 0.35 0.13                          573  0.13   0.73   0.71 11.34                                                                               0.224                                                                               1.72 0.73 0.20 0.18                          574  0.21   0.62   0.42 16.10                                                                               0.006                                                                               0.53 0.42 0.04 0.03                          575  0.16   0.31   0.48 15.72                                                                               0.075                                                                               0.90 0.27 0.06 0.12                          576  0.23   0.05   0.72 7.87 0.252                                                                               2.23 0.10 0.39 0.06                          577  0.06   0.10   0.24 16.61                                                                               0.389                                                                               0.74 0.74 0.24 0.04                          578  0.06   0.35   0.91 7.32 0.818                                                                               2.47 0.55 0.26 0.16                          579  0.03   0.65   0.57 10.25                                                                               0.876                                                                               1.92 0.85 0.37 0.23                          580  0.21   0.11   0.72 10.38                                                                               0.409                                                                               1.88 0.99 0.48 0.12                          ______________________________________                                    

                  TABLE 20-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         551  --       1.163  --     --   --     2.58 1.27                              552  --       0.203  --     --   --     4.02 0.33                              553  0.758    1.720  --     --   --     0.52 0.57                              554  1.744    1.419  --     --   --     1.01 1.73                              555  0.717    1.982  --     --   --     2.27 0.83                              556  1.334    0.065  --     --   --     1.11 0.23                              557  0.274    1.342  --     --   --     3.95 1.47                              558  0.186    1.479  --     --   --     2.80 0.65                              559  --       --     0.968  --   --     1.65 1.95                              560  --       --     0.609  --   --     4.54 1.50                              561  --       --     0.498  --   --     3.47 0.78                              562  --       --     1.290  --   --     4.81 0.42                              563  --       --     1.690  --   --     3.06 1.92                              564  --       --     1.357  --   --     4.57 1.37                              565  1.501    --     1.926  --   --     1.35 1.18                              566  1.464    --     0.140  --   --     4.65 1.97                              567  1.448    --     1.617  --   --     4.04 1.62                              568  0.145    --     0.046  --   --     1.21 1.67                              569  0.196    --     1.116  --   --     4.89 0.89                              570  0.293    --     1.467  --   --     4.74 0.80                              571  --       1.772  0.787  --   --     4.76 0.21                              572  --       0.587  1.743  --   --     1.72 1.49                              573  --       0.327  1.014  --   --     4.49 1.70                              574  --       1.695  1.273  --   --     0.28 1.41                              575  --       0.357  0.190  --   --     0.28 0.34                              576  --       1.963  0.423  --   --     3.72 1.78                              577  0.748    0.217  1.659  --   --     4.99 1.84                              578  1.401    0.776  1.577  --   --     3.29 1.12                              579  0.159    1.287  1.805  --   --     2.67 0.22                              580  0.669    1.461  1.073  --   --     4.73 0.67                              ______________________________________                                    

                  TABLE 20-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         551   0.0015  0.008    0.008                                                                               5       148    17                                  552   0.0267  0.004    0.002                                                                               6       172     8                                  553   0.0026  0.006    0.019                                                                               6       163    32                                  554   0.0141  0.007    0.008                                                                               4       174    29                                  555   0.0117  0.005    0.015                                                                               3       133    27                                  556   0.0051  0.003    0.016                                                                               1       143    23                                  557   0.0043  0.010    0.009                                                                               5       131    18                                  558   0.0048  0.009    0.020                                                                               2       175    22                                  559   0.0162  0.009    0.015                                                                               6       177    18                                  560   0.0189  0.003    0.003                                                                               4       167    19                                  561   0.0078  0.004    0.008                                                                               7       145     9                                  562   0.0080  0.006    0.018                                                                               2       141    16                                  563   0.0296  0.006    0.010                                                                               2       131    23                                  564   0.0226  0.009    0.019                                                                               7       144    20                                  565   0.0272  0.003    0.014                                                                               4       131    35                                  566   0.0237  0.005    0.002                                                                               3       147    17                                  567   0.0067  0.005    0.017                                                                               6       144    35                                  568   0.0019  0.006    0.017                                                                               2       174     8                                  569   0.0037  0.006    0.020                                                                               3       165    22                                  570   0.0074  0.004    0.002                                                                               2       144    25                                  571   0.0084  0.002    0.018                                                                               1       141    29                                  572   0.0012  0.005    0.007                                                                               1       132    25                                  573   0.0263  0.005    0.014                                                                               6       145    24                                  574   0.0189  0.001    0.017                                                                               7       157    28                                  575   0.0038  0.006    0.012                                                                               6       148    18                                  576   0.0061  0.009    0.016                                                                               3       168    31                                  577   0.0210  0.008    0.007                                                                               4       171    29                                  578   0.0134  0.006    0.019                                                                               6       136    36                                  579   0.0085  0.003    0.010                                                                               6       138    39                                  580   0.0162  0.009    0.008                                                                               2       157    33                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 21-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         581  0.26   0.15   0.42 5.47 0.232                                                                               1.78 0.31 0.04 0.01                          582  0.29   0.27   0.73 13.00                                                                               0.693                                                                               1.08 0.61 0.17 0.24                          583  0.09   0.31   0.32 17.77                                                                               0.126                                                                               0.89 0.75 0.31 0.15                          584  0.06   0.56   0.27 11.16                                                                               0.864                                                                               2.33 0.09 0.39 0.19                          585  0.29   0.49   0.83 10.43                                                                               0.250                                                                               3.19 0.90 0.07 0.08                          586  0.02   0.37   0.69 7.15 0.614                                                                               1.28 0.10 0.25 0.15                          587  0.06   0.06   0.51 12.08                                                                               0.794                                                                               1.05 0.95 0.13 0.22                          588  0.07   0.60   0.94 16.45                                                                               0.616                                                                               0.23 0.82 0.34 0.15                          589  0.16   0.71   0.68 11.92                                                                               0.437                                                                               3.29 0.07 0.34 0.02                          590  0.13   0.26   0.78 15.66                                                                               0.573                                                                               3.08 0.49 0.02 0.01                          591  0.22   0.66   0.32 6.08 0.875                                                                               2.37 0.45 0.06 0.10                          592  0.10   0.64   0.77 7.16 0.181                                                                               2.24 0.76 0.11 0.25                          593  0.29   0.44   0.38 16.55                                                                               0.306                                                                               0.50 0.28 0.36 0.17                          594  0.18   0.73   0.63 6.24 0.100                                                                               3.23 0.82 0.46 0.07                          595  0.29   0.20   0.59 6.57 0.893                                                                               1.61 0.74 0.10 0.14                          596  0.28   0.66   0.92 8.93 0.029                                                                               1.71 0.86 0.43 0.24                          597  0.26   0.45   0.31 11.18                                                                               0.341                                                                               1.35 0.53 0.37 0.07                          598  0.17   0.21   0.20 17.68                                                                               0.164                                                                               3.28 0.08 0.10 0.08                          599  0.26   0.19   0.49 13.31                                                                               0.331                                                                               2.03 0.34 0.27 0.23                          600  0.19   0.29   0.22 15.47                                                                               0.684                                                                               1.99 0.16 0.06 0.24                          601  0.06   0.75   0.48 90.00                                                                               0.559                                                                               2.61 0.35 0.38 0.07                          602  0.25   0.27   0.73 11.25                                                                               0.289                                                                               1.71 0.27 0.41 0.04                          603  0.14   0.69   0.84 13.59                                                                               0.208                                                                               0.40 0.25 0.31 0.23                          604  0.26   0.69   0.67 7.38 0.652                                                                               3.06 0.12 0.24 0.13                          605  0.27   0.55   0.90 10.01                                                                               0.958                                                                               0.96 0.71 0.39 0.17                          606  0.13   0.52   1.00 12.72                                                                               0.456                                                                               3.36 0.86 0.15 0.07                          607  0.07   0.48   0.42 13.60                                                                               0.998                                                                               1.58 0.93 0.22 0.16                          608  0.20   0.69   0.66 16.91                                                                               0.910                                                                               1.62 0.25 0.23 0.04                          609  0.03   0.63   0.76 14.01                                                                               0.526                                                                               1.29 0.13 0.14 0.02                          610  0.24   0.57   0.20 9.22 0.685                                                                               3.35 0.90 0.33 0.18                          ______________________________________                                    

                  TABLE 21-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         581  1.622    1.938  0.020  --   --     1.45 0.35                              582  0.687    1.423  1.327  --   --     1.73 1.69                              583  --       --     --     1.260                                                                               --     4.65 1.65                              584  --       --     --     1.256                                                                               --     2.37 0.89                              585  --       --     --     1.984                                                                               --     1.20 1.78                              586  --       --     --     0.122                                                                               --     2.79 0.43                              587  --       --     --     1.345                                                                               --     3.91 1.94                              588  --       --     --     1.320                                                                               --     1.47 0.65                              589  0.546    --     --     0.716                                                                               --     4.16 1.60                              590  0.644    --     --     0.228                                                                               --     1.69 1.86                              591  1.916    --     --     1.515                                                                               --     2.86 0.20                              592  1.005    --     --     0.252                                                                               --     2.05 0.83                              593  1.589    --     --     0.094                                                                               --     3.26 0.77                              594  0.356    --     --     1.712                                                                               --     3.31 0.59                              595  --       1.529  --     1.801                                                                               --     3.84 0.92                              596  --       1.422  --     0.017                                                                               --     4.03 1.45                              597  --       1.391  --     0.041                                                                               --     3.13 1.90                              598  --       1.101  --     1.535                                                                               --     0.31 1.97                              599  --       1.223  --     1.181                                                                               --     2.05 1.38                              600  --       1.421  --     0.639                                                                               --     2.66 0.69                              601  --       --     1.739  1.583                                                                               --     1.42 1.44                              602  --       --     0.303  1.700                                                                               --     2.36 1.54                              603  --       --     1.329  0.655                                                                               --     2.26 0.67                              604  --       --     0.498  0.114                                                                               --     2.76 0.37                              605  --       --     1.481  0.756                                                                               --     3.05 1.21                              606  --       --     0.943  1.241                                                                               --     2.30 1.10                              607  --       0.662  0.552  1.241                                                                               --     4.57 1.55                              608  --       0.723  0.986  0.437                                                                               --     4.28 1.36                              609  --       0.908  1.908  1.479                                                                               --     2.98 1.14                              610  --       1.901  0.016  1.085                                                                               --     2.39 1.50                              ______________________________________                                    

                  TABLE 21-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         581   0.0168  0.002    0.017                                                                               0       170    35                                  582   0.0054  0.001    0.016                                                                               3       154    38                                  583   0.0068  0.002    0.002                                                                               6       138    15                                  584   0.0015  0.006    0.019                                                                               4       149    19                                  585   0.0291  0.009    0.017                                                                               7       164    26                                  586   0.0103  0.004    0.001                                                                               2       163     9                                  587   0.0143  0.003    0.017                                                                               0       172    18                                  588   0.0221  0.004    0.013                                                                               3       169    16                                  589   0.0280  0.007    0.005                                                                               5       156    22                                  590   0.0276  0.005    0.010                                                                               7       138    19                                  591   0.0161  0.001    0.006                                                                               6       141    33                                  592   0.0032  0.008    0.017                                                                               5       142    21                                  593   0.0289  0.010    0.012                                                                               6       171    25                                  594   0.0283  0.010    0.007                                                                               6       154    30                                  595   0.0268  0.007    0.017                                                                               2       169    32                                  596   0.0193  0.003    0.003                                                                               7       144    19                                  597   0.0009  0.008    0.017                                                                               3       157    17                                  598   0.0265  0.009    0.018                                                                               6       160    28                                  599   0.0167  0.010    0.013                                                                               5       157    27                                  600   0.0257  0.009    0.018                                                                               2       149    29                                  601   0.0193  0.005    0.010                                                                               6       140    34                                  602   0.0224  0.006    0.006                                                                               5       158    25                                  603   0.0152  0.001    0.012                                                                               6       179    27                                  604   0.0076  0.007    0.015                                                                               0       132    10                                  605   0.0247  0.008    0.003                                                                               4       170    27                                  606   0.0015  0.003    0.020                                                                               2       170    25                                  607   0.0229  0.009    0.015                                                                               0       135    29                                  608   0.0095  0.010    0.014                                                                               2       143    27                                  609   0.0159  0.010    0.003                                                                               4       172    38                                  610   0.0075  0.007    0.010                                                                               4       173    33                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 22-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         611  0.06   0.75   0.85 6.96 0.221                                                                               0.67 0.93 0.24 0.13                          612  0.16   0.68   0.97 5.05 0.465                                                                               0.93 0.06 0.28 0.07                          613  0.20   0.61   0.85 14.50                                                                               0.765                                                                               0.34 0.09 0.13 0.20                          614  0.15   0.40   0.74 13.63                                                                               0.956                                                                               3.29 0.87 0.43 0.24                          615  0.24   0.73   0.92 6.76 0.871                                                                               0.98 0.26 0.38 0.03                          616  0.27   0.28   0.85 11.21                                                                               0.341                                                                               1.10 0.06 0.14 0.12                          617  0.07   0.10   0.80 11.88                                                                               0.697                                                                               1.47 0.61 0.36 0.01                          618  0.15   0.43   0.23 6.61 0.290                                                                               3.21 0.27 0.23 0.13                          619  0.18   0.40   0.63 12.80                                                                               0.940                                                                               2.46 0.84 0.15 0.20                          620  0.11   0.25   0.26 15.43                                                                               0.505                                                                               0.37 0.22 0.30 0.18                          621  0.19   0.25   0.58 5.71 0.799                                                                               1.30 0.18 0.10 0.04                          622  0.08   0.26   0.26 7.56 0.172                                                                               1.43 0.09 0.20 0.09                          623  0.17   0.16   0.78 5.84 0.449                                                                               0.22 0.76 0.29 0.06                          624  0.11   0.61   0.41 11.42                                                                               0.473                                                                               0.43 0.06 0.27 0.14                          625  0.16   0.69   0.60 9.18 0.081                                                                               1.51 0.79 0.07 0.06                          626  0.25   0.27   0.43 9.97 0.104                                                                               2.91 0.33 0.11 0.13                          627  0.21   0.79   0.58 11.66                                                                               0.378                                                                               0.82 0.96 0.29 0.20                          628  0.13   0.57   0.50 12.18                                                                               0.247                                                                               1.29 0.58 0.30 0.23                          629  0.10   0.63   0.47 15.79                                                                               0.038                                                                               2.10 0.96 0.05 0.17                          630  0.22   0.08   0.34 7.35 0.583                                                                               2.72 .0.98                                                                               0.44 0.24                          631  0.02   0.34   0.81 17.28                                                                               0.726                                                                               0.96 0.48 0.17 0.14                          632  0.30   0.50   0.92 10.90                                                                               0.297                                                                               2.86 0.26 0.13 0.08                          633  0.01   0.45   0.95 5.68 0.645                                                                               1.34 0.67 0.50 0.15                          634  0.27   0.06   0.38 5.99 0.101                                                                               2.42 0.08 0.45 0.17                          635  0.16   0.75   0.27 9.63 0.992                                                                               0.62 0.77 0.15 0.12                          636  0.05   0.43   0.88 7.89 0.657                                                                               0.30 0.12 0.26 0.19                          637  0.05   0.56   0.89 11.77                                                                               0.438                                                                               0.98 0.44 0.20 0.22                          638  0.12   0.23   0.96 6.15 0.172                                                                               2.10 0.58 0.15 0.18                          639  0.20   0.07   0.97 8.23 0.674                                                                               3.08 0.36 0.25 0.02                          640  0.10   0.74   0.38 9.49 0.309                                                                               3.44 0.15 0.20 0.07                          ______________________________________                                    

                  TABLE 22-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         611  --       1.381  0.967  0.900                                                                               --     1.64 0.34                              612  --       0.010  0.436  1.594                                                                               --     2.40 1.87                              613  1.738    --     1.064  0.821                                                                               --     3.80 1.28                              614  0.015    --     0.569  1.286                                                                               --     2.72 1.88                              615  0.557    --     0.610  1.656                                                                               --     0.78 0.70                              616  0.062    --     1.833  1.572                                                                               --     1.89 1.89                              617  1.170    --     0.944  0.755                                                                               --     0.64 0.72                              618  1.575    --     0.590  1.822                                                                               --     3.24 1.33                              619  1.956    0.861  --     1.500                                                                               --     1.90 0.79                              620  0.979    0.857  --     1.441                                                                               --     0.52 0.56                              621  0.312    1.024  --     1.287                                                                               --     3.11 0.36                              622  1.631    1.064  --     0.743                                                                               --     4.11 0.79                              623  0.603    0.650  --     1.475                                                                               --     2.74 0.66                              624  0.890    1.443  --     1.153                                                                               --     2.98 1.46                              625  0.186    0.115  0.895  0.440                                                                               --     1.67 0.21                              626  0.151    0.336  0.101  1.003                                                                               --     2.78 1.11                              627  0.464    1.771  0.887  0.537                                                                               --     0.78 1.17                              628  1.782    0.127  1.952  0.700                                                                               --     4.45 0.98                              629  1.789    0.039  0.951  0.176                                                                               --     1.03 0.27                              630  0.150    0.207  1.569  1.629                                                                               --     1.74 1.42                              631  0.528    --     --     --   2.19   0.92 1.45                              632  1.613    --     --     --   1.89   0.24 1.85                              633  0.079    --     --     --   2.42   3.69 0.54                              634  0.592    --     --     --   3.05   0.91 0.81                              635  0.808    --     --     --   2.96   3.10 0.59                              636  1.428    --     --     --   1.37   4.66 1.36                              637  --       1.490  --     --   2.29   4.81 1.02                              638  --       1.763  --     --   2.49   0.33 1.99                              639  --       1.309  --     --   3.66   2.50 1.27                              640  --       1.828  --     --   2.54   3.24 0.35                              ______________________________________                                    

                  TABLE 22-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         611   0.0243  0.004    0.011                                                                               6       176    35                                  612   0.0015  0.009    0.013                                                                               7       132    27                                  613   0.0087  0.007    0.012                                                                               4       170    37                                  614   0.0263  0.010    0.006                                                                               4       142    24                                  615   0.0050  0.007    0.020                                                                               6       176    28                                  616   0.0134  0.005    0.013                                                                               1       175    34                                  617   0.0031  0.009    0.019                                                                               6       166    29                                  618   0.0129  0.002    0.017                                                                               2       152    41                                  619   0.0240  0.007    0.013                                                                               3       161    37                                  620   0.0158  0.007    0.013                                                                               6       145    39                                  621   0.0137  0.006    0.015                                                                               4       133    34                                  622   0.0127  0.003    0.015                                                                               2       152    31                                  623   0.0077  0.009    0.010                                                                               4       179    29                                  624   0.0089  0.010    0.006                                                                               4       144    31                                  625   0.0112  0.008    0.019                                                                               1       172    27                                  626   0.0099  0.007    0.009                                                                               1       143    24                                  627   0.0003  0.005    0.010                                                                               2       133    42                                  628   0.0069  0.009    0.018                                                                               5       171    40                                  629   0.0251  0.010    0.013                                                                               0       133    35                                  630   0.0202  0.009    0.009                                                                               1       174    38                                  631   0.0020  0.002    0.013                                                                               5       170    10                                  632   0.0104  0.005    0.013                                                                               6       175    19                                  633   0.0109  0.007    0.005                                                                               2       166    12                                  634   0.0281  0.006    0.005                                                                               6       171    12                                  635   0.0127  0.002    0.001                                                                               2       142    19                                  636   0.0043  0.006    0.018                                                                               4       158    24                                  637   0.0130  0.008    0.005                                                                               6       171    24                                  638   0.0188  0.006    0.007                                                                               5       158    25                                  639   0.0025  0.008    0.011                                                                               6       149    17                                  640   0.0030  0.004    0.005                                                                               1       144    23                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 23-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         641  0.07   0.17   0.66 14.30                                                                               0.390                                                                               0.93 0.23 0.14 0.04                          642  0.20   0.18   0.47 14.07                                                                               0.774                                                                               3.34 0.50 0.26 0.02                          643  0.30   0.65   0.91 13.22                                                                               0.294                                                                               3.48 0.75 0.47 0.09                          644  0.17   0.65   0.61 15.86                                                                               0.761                                                                               0.77 0.84 0.19 0.20                          645  0.06   0.06   0.27 7.07 0.039                                                                               1.33 0.60 0.09 0.08                          646  0.22   0.33   0.54 10.71                                                                               0.948                                                                               1.29 0.85 0.32 0.17                          647  0.01   0.15   0.50 51.0 0.336                                                                               1.78 0.46 0.07 0.08                          648  0.11   0.17   0.40 7.60 0.529                                                                               0.58 0.73 0.49 0.22                          649  0.19   0.25   0.93 9.53 0.359                                                                               0.44 0.51 0.02 0.11                          650  0.19   0.28   0.35 15.27                                                                               0.173                                                                               0.85 0.15 0.06 0.04                          651  0.21   0.13   0.52 16.32                                                                               0.798                                                                               2.91 0.46 0.28 0.22                          652  0.21   0.05   0.92 16.90                                                                               0.086                                                                               1.14 0.29 0.35 0.02                          653  0.29   0.71   0.63 15.04                                                                               0.360                                                                               3.24 0.97 0.44 0.11                          654  0.10   0.41   0.69 8.44 0.952                                                                               0.41 0.86 0.23 0.22                          655  0.17   0.59   0.60 8.03 0.211                                                                               2.00 0.27 0.12 0.18                          656  0.18   0.33   0.99 11.57                                                                               0.949                                                                               0.86 0.04 0.03 0.19                          657  0.22   0.29   0.57 17.19                                                                               0.536                                                                               3.10 0.99 0.37 0.22                          658  0.09   0.34   0.38 9.48 0.282                                                                               1.54 0.99 0.09 0.23                          659  0.19   0.36   0.70 12.49                                                                               0.532                                                                               2.26 0.87 0.07 0.05                          660  0.02   0.21   0.20 11.01                                                                               0.622                                                                               1.39 0.45 0.25 0.01                          661  0.28   0.16   0.75 9.37 0.385                                                                               3.33 0.07 0.29 0.19                          662  0.17   0.46   0.21 11.99                                                                               0.656                                                                               2.64 0.07 0.36 0.19                          663  0.11   0.22   0.85 16.73                                                                               0.273                                                                               0.38 0.76 0.38 0.09                          664  0.16   0.07   0.94 8.41 0.574                                                                               0.99 0.04 0.28 0.09                          665  0.02   0.30   0.76 17.55                                                                               0.400                                                                               0.62 0.67 0.20 0.15                          666  0.20   0.36   0.97 9.41 0.081                                                                               2.04 0.06 0.33 0.11                          667  0.07   0.55   0.24 14.37                                                                               0.947                                                                               3.03 0.96 0.33 0.17                          668  0.03   0.32   0.83 17.23                                                                               0.339                                                                               1.41 0.30 0.36 0.17                          669  0.03   0.72   0.62 15.87                                                                               0.096                                                                               1.59 0.34 0.11 0.08                          670  0.16   0.07   0.67 14.75                                                                               0.548                                                                               3.03 0.94 0.47 0.09                          ______________________________________                                    

                  TABLE 23-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         641  --       0.967  --     --   0.82   4.30 0.78                              642  --       0.431  --     --   2.47   4.79 1.33                              643  1.039    0.860  --     --   1.92   1.56 0.81                              644  1.958    1.934  --     --   0.75   0.99 1.63                              645  0.320    1.331  --     --   0.57   4.70 0.76                              646  0.776    1.709  --     --   3.01   2.31 0.66                              647  1.028    0.752  --     --   2.48   2.63 1.00                              648  1.708    1.127  --     --   3.02   2.50 1.49                              649  --       --     1.216  --   1.42   1.11 0.95                              650  --       --     0.082  --   4.09   4.87 1.77                              651  --       --     0.652  --   0.62   0.97 1.84                              652  --       --     0.621  --   4.67   3.08 0.90                              653  --       --     1.640  --   1.01   0.75 0.43                              654  --       --     1.396  --   3.27   0.43 1.93                              655  1.643    --     1.563  --   1.07   1.32 1.53                              656  1.141    --     1.798  --   3.23   0.26 0.72                              657  0.131    --     0.793  --   4.13   1.22 1.01                              658  0.304    --     0.200  --   0.60   3.44 1.19                              659  0.304    --     0.704  --   3.87   1.33 1.88                              660  1.823    --     1.946  --   3.48   3.63 1.85                              661  --       0.176  1.644  --   1.16   2.52 0.88                              662  --       0.786  1.458  --   3.26   1.88 0.41                              663  --       0.819  1.059  --   4.22   3.38 1.07                              664  --       1.909  0.090  --   3.16   1.36 0.75                              665  --       0.777  0.258  --   4.20   2.31 0.97                              666  --       0.072  0.221  --   4.11   3.01 0.53                              667  1.272    1.462  1.647  --   4.49   2.64 0.92                              668  0.081    1.588  0.181  --   4.48   2.79 1.83                              669  1.461    1.159  1.159  --   0.97   2.71 1.19                              670  1.063    1.859  1.360  --   0.47   4.15 0.54                              ______________________________________                                    

                  TABLE 23-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         641   0.0015  0.005    0.013                                                                               6       172    20                                  642   0.0224  0.005    0.015                                                                               3       161    17                                  643   0.0162  0.008    0.006                                                                               1       139    22                                  644   0.0226  0.007    0.002                                                                               2       133    39                                  645   0.0067  0.006    0.011                                                                               2       171    19                                  646   0.0088  0.007    0.009                                                                               6       180    31                                  647   0.0089  0.009    0.003                                                                               7       139    22                                  648   0.0021  0.002    0.010                                                                               6       174    32                                  649   0.0132  0.002    0.006                                                                               0       165    18                                  650   0.0228  0.008    0.009                                                                               1       139    10                                  651   0.0107  0.004    0.014                                                                               7       173    11                                  652   0.0018  0.008    0.019                                                                               4       170    11                                  653   0.0213  0.008    0.020                                                                               4       158    18                                  654   0.0045  0.003    0.005                                                                               7       164    19                                  655   0.0212  0.001    0.009                                                                               4       167    35                                  656   0.0068  0.005    0.009                                                                               4       143    30                                  657   0.0010  0.004    0.013                                                                               0       147    13                                  658   0.0288  0.001    0.016                                                                               1       155    14                                  659   0.0259  0.009    0.017                                                                               5       170    13                                  660   0.0165  0.003    0.010                                                                               5       170    37                                  661   0.0118  0.009    0.004                                                                               6       133    28                                  662   0.0061  0.008    0.014                                                                               0       161    26                                  663   0.0245  0.001    0.009                                                                               0       132    21                                  664   0.0173  0.007    0.003                                                                               2       149    30                                  665   0.0243  0.005    0.014                                                                               4       140    20                                  666   0.0261  0.008    0.009                                                                               1       132     8                                  667   0.0022  0.009    0.013                                                                               7       154    48                                  668   0.0222  0.007    0.015                                                                               5       132    20                                  669   0.0074  0.010    0.002                                                                               4       145    45                                  670   0.0275  0.007    0.008                                                                               7       170    47                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 24-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         671  0.09   0.57   0.86 5.19 0.536                                                                               1.89 0.96 0.38 0.17                          672  0.06   0.16   0.25 17.61                                                                               0.897                                                                               2.60 0.23 0.50 0.15                          673  0.16   0.65   0.72 17.33                                                                               0.464                                                                               1.27 0.55 0.25 0.12                          674  0.07   0.73   0.52 8.61 0.571                                                                               0.70 0.29 0.05 0.15                          675  0.02   0.30   0.33 15.51                                                                               0.063                                                                               1.98 0.28 0.06 0.21                          676  0.25   0.38   0.82 16.27                                                                               0.759                                                                               1.27 0.34 0.20 0.02                          677  0.13   0.07   0.65 8.78 0.012                                                                               1.33 0.81 0.39 0.01                          678  0.06   0.03   0.50 16.98                                                                               0.150                                                                               1.62 0.55 0.06 0.04                          679  0.28   0.12   0.64 12.62                                                                               0.008                                                                               1.61 0.87 0.11 0.05                          680  0.16   0.60   0.53 13.18                                                                               0.919                                                                               0.73 0.62 0.45 0.14                          681  0.08   0.57   0.43 16.48                                                                               0.239                                                                               3.42 0.14 0.28 0.13                          682  0.15   0.29   0.63 13.87                                                                               0.277                                                                               0.88 0.25 0.25 0.24                          683  0.02   0.41   0.59 16.07                                                                               0.377                                                                               2.42 0.27 0.02 0.06                          684  0.08   0.02   0.97 8.22 0.880                                                                               2.63 0.58 0.02 0.15                          685  0.15   0.56   0.85 14.11                                                                               0.131                                                                               2.58 0.99 0.16 0.24                          686  0.17   0.35   0.50 5.62 0.952                                                                               1.74 0.85 0.12 0.04                          687  0.24   0.40   0.97 12.92                                                                               0.675                                                                               1.16 0.48 0.06 0.23                          688  0.17   0.23   0.96 8.12 0.651                                                                               0.38 0.23 0.38 0.18                          689  0.20   0.07   0.31 13.99                                                                               0.707                                                                               2.13 0.91 0.04 0.08                          690  0.28   0.20   0.51 5.39 0.677                                                                               0.89 0.39 0.41 0.02                          691  0.22   0.48   0.99 15.95                                                                               0.884                                                                               2.69 0.96 0.44 0.07                          692  0.12   0.78   0.46 5.78 0.681                                                                               2.08 0.50 0.04 0.09                          693  0.07   0.21   0.38 11.85                                                                               0.914                                                                               0.24 0.35 0.13 0.14                          694  0.03   0.20   0.22 6.02 0.414                                                                               3.17 0.81 0.14 0.07                          695  0.10   0.23   0.64 12.12                                                                               0.513                                                                               2.09 0.75 0.45 0.20                          696  0.08   0.17   0.72 14.91                                                                               0.043                                                                               3.03 0.98 0.03 0.14                          697  0.08   0.28   0.72 5.86 0.342                                                                               0.53 0.86 0.49 0.19                          698  0.18   0.43   0.91 8.83 0.252                                                                               0.64 0.22 0.30 0.08                          699  0.05   0.50   0.36 8.64 0.098                                                                               1.13 0.86 0.10 0.02                          700  0.22   0.73   0.53 9.51 0.714                                                                               1.50 0.17 0.06 0.08                          ______________________________________                                    

                  TABLE 24-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         671  0.585    0.375  1.370  --   2.11   3.79 1.36                              672  1.672    1.328  1.207  --   2.69   3.25 1.53                              673  --       --     --     1.975                                                                               1.41   4.13 0.77                              674  --       --     --     1.491                                                                               2.36   0.92 0.61                              675  --       --     --     0.211                                                                               2.28   4.76 1.62                              676  --       --     --     0.808                                                                               0.37   0.46 1.70                              677  --       --     --     0.951                                                                               3.09   4.04 0.58                              678  --       --     --     0.321                                                                               2.40   0.32 0.64                              679  0.907    --     --     0.578                                                                               4.75   2.92 1.60                              680  1.795    --     --     1.402                                                                               2.14   3.85 1.38                              681  0.320    --     --     0.487                                                                               3.42   4.74 1.46                              682  1.134    --     --     1.480                                                                               2.97   4.79 0.66                              683  0.888    --     --     1.045                                                                               2.37   0.76 1.37                              684  1.317    --     --     1.871                                                                               0.88   3.93 1.50                              685  --       0.402  --     1.643                                                                               4.94   3.92 1.67                              686  --       0.344  --     1.999                                                                               4.09   4.66 0.65                              687  --       1.828  --     1.636                                                                               2.38   3.08 0.89                              688  --       1.534  --     1.224                                                                               1.44   0.72 0.27                              689  --       0.116  --     0.414                                                                               2.81   3.94 0.28                              690  --       0.232  --     0.888                                                                               0.98   4.86 0.65                              691  --       --     0.816  1.329                                                                               4.74   2.62 1.96                              692  --       --     1.278  1.395                                                                               3.65   1.26 1.24                              693  --       --     0.685  1.771                                                                               4.21   2.40 1.79                              694  --       --     1.689  1.116                                                                               3.20   2.85 1.50                              695  --       --     0.985  0.118                                                                               2.21   4.22 0.99                              696  --       --     1.222  1.416                                                                               0.44   0.87 1.75                              697  --       1.047  0.086  1.724                                                                               4.36   4.11 0.80                              698  --       1.789  1.247  1.695                                                                               1.16   1.09 0.54                              699  --       1.128  1.370  1.991                                                                               4.41   3.02 0.67                              700  --       1.750  0.152  1.312                                                                               3.81   1.97 0.90                              ______________________________________                                    

                  TABLE 24-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S        O    D-CRS   HAZCRS M %                                 ______________________________________                                         671   0.0028  0.005    0.011                                                                               3       135    31                                  672   0.0178  0.008    0.009                                                                               6       168    43                                  673   0.0078  0.001    0.017                                                                               6       146    29                                  674   0.0281  0.005    0.013                                                                               0       173    17                                  675   0.0285  0.004    0.013                                                                               4       175    15                                  676   0.0042  0.006    0.014                                                                               2       156    19                                  677   0.0250  0.001    0.013                                                                               1       144    15                                  678   0.0261  0.001    0.015                                                                               5       141     7                                  679   0.0179  0.004    0.019                                                                               6       175    21                                  680   0.0253  0.010    0.010                                                                               6       148    32                                  681   0.0135  0.006    0.016                                                                               5       139    11                                  682   0.0221  0.001    0.004                                                                               3       150    26                                  683   0.0017  0.003    0.018                                                                               5       158    22                                  684   0.0220  0.005    0.008                                                                               6       168    33                                  685   0.0186  0.006    0.009                                                                               5       156    22                                  686   0.0158  0.009    0.007                                                                               5       150    23                                  687   0.0245  0.008    0.001                                                                               1       152    38                                  688   0.0244  0.002    0.006                                                                               2       141    31                                  689   0.0252  0.006    0.009                                                                               4       169    16                                  690   0.0077  0.002    0.017                                                                               2       165    21                                  691   0.0262  0.006    0.007                                                                               5       155    28                                  692   0.0165  0.008    0.015                                                                               6       167    26                                  693   0.0184  0.001    0.008                                                                               6       155    29                                  694   0.0120  0.007    0.013                                                                               1       170    27                                  695   0.0221  0.002    0.007                                                                               7       167    16                                  696   0.0291  0.002    0.006                                                                               2       146    27                                  697   0.0281  0.010    0.016                                                                               6       137    35                                  698   0.0141  0.002    0.015                                                                               4       167    48                                  699   0.0269  0.004    0.010                                                                               6       163    39                                  700   0.0172  0.006    0.017                                                                               5       154    37                                  ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                  TABLE 25-1                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  C      Si     Mn   Cr   Mo   W    V    Nb   N                             ______________________________________                                         701  0.21   0.24   0.91 9.56 0.450                                                                               2.84 0.43 0.35 0.10                          702  0.11   0.45   0.54 6.45 0.127                                                                               2.97 0.52 0.39 0.17                          703  0.04   0.06   0.91 17.65                                                                               0.088                                                                               2.98 0.27 0.11 0.12                          704  0.07   0.50   0.68 15.12                                                                               0.185                                                                               2.36 0.99 0.40 0.15                          705  0.02   0.09   0.92 9.65 0.220                                                                               0.56 0.55 0.45 0.11                          706  0.28   0.26   0.70 5.48 0.547                                                                               1.95 0.26 0.42 0.08                          707  0.08   0.10   0.29 13.64                                                                               0.508                                                                               2.73 0.47 0.23 0.13                          708  0.08   0.26   0.36 6.01 0.935                                                                               2.36 1.00 0.30 0.24                          709  0.25   0.61   0.78 6.28 0.160                                                                               0.27 0.21 0.29 0.23                          710  0.25   0.25   0.61 6.03 0.523                                                                               0.90 0.42 0.13 0.19                          711  0.02   0.23   0.93 9.59 0.862                                                                               2.06 0.48 0.23 0.08                          712  0.26   0.79   0.39 8.10 0.500                                                                               1.49 0.20 0.50 0.09                          713  0.03   0.64   0.88 12.65                                                                               0.286                                                                               2.04 0.92 0.38 0.08                          714  0.01   0.05   0.66 8.10 0.055                                                                               3.13 0.02 0.27 0.13                          715  0.02   0.05   0.39 5.22 0.632                                                                               0.88 0.28 0.10 0.18                          716  0.30   0.53   0.76 8.47 0.369                                                                               3.08 0.07 0.02 0.08                          717  0.07   0.17   0.42 9.12 0.586                                                                               0.88 0.70 0.21 0.16                          718  0.30   0.03   0.45 11.69                                                                               0.139                                                                               2.02 0.04 0.34 0.02                          719  0.22   0.37   0.31 13.79                                                                               0.332                                                                               0.94 0.87 0.08 0.20                          720  0.07   0.65   0.66 13.50                                                                               0.034                                                                               2.15 0.11 0.09 0.09                          ______________________________________                                    

                  TABLE 25-2                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.  Ti       Zr     Ta     Hf   Co     Ni   Cu                                ______________________________________                                         701  --       1.320  1.239  1.310                                                                               3.31   1.89 1.83                              702  --       1.487  0.298  1.641                                                                               2.09   2.01 0.47                              703  1.220    --     0.025  1.004                                                                               4.23   3.95 1.02                              704  1.510    --     0.055  0.054                                                                               1.70   4.49 1.37                              705  1.549    --     1.089  1.455                                                                               0.90   0.46 0.35                              706  1.018    --     0.804  0.923                                                                               1.13   0.73 1.26                              707  1.560    --     1.858  0.093                                                                               1.51   2.03 1.99                              708  0.886    --     1.929  0.641                                                                               3.71   3.61 0.46                              709  0.631    1.371  --     1.234                                                                               2.11   2.30 1.77                              710  1.504    0.654  --     0.556                                                                               0.72   4.48 1.13                              711  1.160    0.598  --     0.273                                                                               3.54   4.56 0.92                              712  1.235    1.864  --     1.048                                                                               0.22   1.76 1.77                              713  1.457    1.158  --     1.581                                                                               4.39   4.95 1.59                              714  0.470    0.131  --     1.527                                                                               0.82   1.28 0.97                              715  0.946    0.427  0.199  0.537                                                                               0.68   4.31 1.40                              716  0.571    0.776  0.577  1.322                                                                               0.90   1.37 0.81                              717  1.005    1.793  1.990  0.532                                                                               3.01   3.62 0.71                              718  0.923    1.196  1.157  1.843                                                                               1.45   0.69 1.69                              719  0.972    1.619  0.713  1.907                                                                               2.57   3.69 0.72                              720  1.877    1.728  0.321  1.400                                                                               0.80   4.72 0.25                              ______________________________________                                    

                  TABLE 25-3                                                       ______________________________________                                         STEEL OF INVENTION                                                             (Mass. %)                                                                      No.   P       S       O    D-CRS   HAZCRS M %                                  ______________________________________                                         701   0.0096  0.010   0.003                                                                               6       166    39                                   702   0.0291  0.010   0.004                                                                               3       179    32                                   703   0.0261  0.009   0.007                                                                               2       169    31                                   704   0.0253  0.006   0.009                                                                               5       164    21                                   705   0.0221  0.005   0.007                                                                               5       167    40                                   706   0.0117  0.002   0.017                                                                               3       131    34                                   707   0.0040  0.007   0.007                                                                               6       134    41                                   708   0.0088  0.008   0.003                                                                               5       152    35                                   709   0.0064  0.004   0.010                                                                               6       165    38                                   710   0.0220  0.007   0.008                                                                               4       149    32                                   711   0.0205  0.002   0.001                                                                               3       133    26                                   712   0.0270  0.001   0.016                                                                               4       144    36                                   713   0.0220  0.003   0.012                                                                               6       159    42                                   714   0.0151  0.002   0.013                                                                               4       158    29                                   715   0.0162  0.004   0.017                                                                               5       166    29                                   716   0.0208  0.009   0.002                                                                               7       138    30                                   717   0.0240  0.007   0.002                                                                               2       176    52                                   718   0.0208  0.008   0.006                                                                               2       157    46                                   719   0.0206  0.004   0.018                                                                               0       159    46                                   720   0.0044  0.009   0.017                                                                               2       161    52                                   ______________________________________                                          D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

                                      TABLE 26-1                                   __________________________________________________________________________     COMPARATIVE STEEL                                                              (Mass. %)                                                                      C     Si Mn Cr Mo W  V  Nb N  Ti Zr Ta Hf Co                                   __________________________________________________________________________     721                                                                               0.096                                                                             0.637                                                                             0.307                                                                             13.8                                                                              0.32                                                                              2.21                                                                              0.540                                                                             0.144                                                                             0.026                                                                             1.974                                                                             -- 0.797                                                                             -- --                                   722                                                                               0.063                                                                             0.070                                                                             0.862                                                                             17.3                                                                              0.04                                                                              0.52                                                                              0.205                                                                             0.011                                                                             0.022                                                                             -  1.546                                                                             -- -- 0.67                                 723                                                                               0.025                                                                             0.520                                                                             0.599                                                                             10.8                                                                              0.95                                                                              1.57                                                                              0.684                                                                             0.150                                                                             0.217                                                                             -- 0.002                                                                             -- -- --                                   724                                                                               0.072                                                                             0.339                                                                             0.461                                                                             8.0                                                                               0.94                                                                              2.50                                                                              0.538                                                                             0.211                                                                             0.194                                                                             -- -- -- -- 4.29                                 725                                                                               0.077                                                                             0.187                                                                             0.497                                                                             12.4                                                                              0.27                                                                              3.22                                                                              0.913                                                                             0.286                                                                             0.222                                                                             2.243                                                                             0.252                                                                             -- 0.001                                                                             2.95                                 726                                                                               0.012                                                                             0.016                                                                             0.994                                                                             14.6                                                                              0.60                                                                              2.15                                                                              0.099                                                                             0.061                                                                             0.170                                                                             -- 3.105                                                                             -- -- 1.86                                 727                                                                               0.117                                                                             0.032                                                                             0.495                                                                             6.2                                                                               0.39                                                                              0.33                                                                              0.372                                                                             0.035                                                                             0.175                                                                             -- -- 2.007                                                                             -- --                                   728                                                                               0.109                                                                             0.195                                                                             0.328                                                                             16.2                                                                              0.74                                                                              0.69                                                                              0.534                                                                             0.060                                                                             0.090                                                                             -- -- 1.559                                                                             3.511                                                                             4.15                                 729                                                                               0.276                                                                             0.777                                                                             0.640                                                                             13.3                                                                              0.01                                                                              2.61                                                                              0.811                                                                             0.253                                                                             0.016                                                                             1.938                                                                             -- 1.287                                                                             -- --                                   730                                                                               0.066                                                                             0.013                                                                             0.265                                                                             5.0                                                                               0.16                                                                              3.00                                                                              0.480                                                                             0.229                                                                             0.131                                                                             -- 1.535                                                                             -- 0.180                                                                             1.56                                 __________________________________________________________________________

                                      TABLE 26-2                                   __________________________________________________________________________     COMPARATIVE STEEL                                                              (Mass. %)                                                                                                     Addition time of Ti, Zr,                        Ni    Cu P  S  O  D-CRS                                                                              HAZCRS                                                                              M % Ta and Hf                                       __________________________________________________________________________     721                                                                               4.76                                                                              -- 0.015                                                                             0.004                                                                             0.006                                                                             42  84   0   During melting step                             722                                                                               -- -- 0.014                                                                             0.009                                                                             0.006                                                                             77  105  1   During melting step                             723                                                                               -- 1.24                                                                              0.009                                                                             0.001                                                                             0.010                                                                             81  77   2   During refining step,                                                          10 min. before tapping                          724                                                                               -- 1.57                                                                              0.008                                                                             0.008                                                                             0.013                                                                             42  80   0   During refining step,                                                          10 min. before tapping                          725                                                                               -- -- 0.022                                                                             0.04                                                                              0.14                                                                              54  91   71  During refining step,                                                          10 min. before tapping                          726                                                                               -- 1.52                                                                              0.024                                                                             0.003                                                                             0.011                                                                             25  85   84  During refining step,                                                          10 min. before tapping                          727                                                                               0.90                                                                              1.97                                                                              0.023                                                                             0.001                                                                             0.008                                                                             40  93   90  During refining step,                                                          10 min. before tapping                          728                                                                               2.23                                                                              -- 0.017                                                                             0.002                                                                             0.016                                                                             39  106  68  During refining step,                                                          10 min. before tapping                          729                                                                               -- -- 0.016                                                                             0.003                                                                             0.001                                                                             29  100  2   During refining step,                                                          10 min. before tapping                          730                                                                               3.56                                                                              1.65                                                                              0.012                                                                             0.003                                                                             0.006                                                                             36  98   2   During refining step,                                                          10 min. before tapping                          __________________________________________________________________________      D-CRS: Difference between the creep rupture strength at 600° C. fo      100,000 hours estimated by linear extrapolation of a base steel and that       of a weld heataffected zone (MPa)                                              HAZCRS: Creep rupture strength of a weld zone at 600° C. for            100,000 hours estimated by linear extrapolation (MPa)                          M %: Value of (Ti % + Zr % + Ta % + Hf %) in M of M.sub.23 C.sub.6 type        carbides in a weld heataffected zone                                     

POSSIBILITY OF UTILIZATION IN THE INDUSTRY

As described above in detail, the present invention provides a martensitic heat-resisting steel excellent in HAZ-softening resistance and exhibiting a high creep strength at high temperature of at least 550° C. The present invention can, therefore, provide materials at low cost which can withstand operation conditions at high temperature and high pressure in thermal power plant boilers, etc. Accordingly, the present invention extremely contributes to the development of the industry. 

We claim:
 1. A martensitic heat-resisting steel having a tempered martensite structure and excellent in HAZ-softening resistance consisting essentially of, in terms of % by mass, 0.01 to 0.30% of C, 0.02 to 0.80% of Si, 0.20 to 1.00% of Mn, 5.00 to 18.00% of Cr, 0.005 to 1.00% of Mo, 0.20 to 3.50% of W, 0.02 to 1.00% of V, 0.01 to 0.50% of Nb, 0.01 to 0.25% of N, up to 0.030% of P, up to 0.010% of S, up to 0.020% of O, at least one element selected from the group consisting of Ti, Zr, Ta and Hf in an amount of 0.005 to 2.0% for each of the elements, and the balance Fe and unavoidable impurities, the volume of (Ti %+Zr %+Ta %+Hf %) in the metal component M of M₂₃ C₆ type carbides precipitated in the tempered martensite structure of the steel being from 5 to 65%.
 2. The martensitic heat-resisting steel according to claim 1, wherein said steel further consists essentially of, in terms of % by mass, at least one element selected from the group consisting of Co, Ni and Cu in an amount of 0.1 to 5.0% for Co or Ni, and 0.1 to 2.0% for Cu.
 3. A process for producing a martensitic heat-resisting steel excellent in HAZ-softening resistance, comprising the steps ofadding at least one element selected from the group consisting of Ti, Zr, Ta and Hf in an amount of 0.005 to 2.0% for each of the elements, in terms of % by mass, to a molten steel consisting essentially of 0.01 to 0.30% of C, 0.02 to 0.80% of Si, 0.20 to 1.00% of Mn, 5.00 to 18.00% of Cr, 0.005 to 1.00% of Mo, 0.20 to 3.50% of W, 0.02 to 1.00% of V, 0.01 to 0.50% of Nb, 0.01 to 0.25% of N, up to 0.030% of P, up to 0.010% of S, up to 0.020% of O, and the balance Fe and unavoidable impurities, during the period from 10 minutes before completion of refining to completion of refining, casting said molten steel, hot working the resulting casting, solution treating the hot worked product thus obtained, subjecting said hot worked product having been solution treated to cooling stop at a temperature from 950° to 1,000° C. in the course of cooling said hot worked product from the solution treating temperature to room temperature, holding said hot worked product at the temperature for 5 to 60 minutes, and tempering said worked product.
 4. The process for producing a martensitic heat-resisting steel according to claim 3, wherein said molten steel further consisting essentially of, in terms of % by mass, at least one element selected from the group consisting of Co, Ni and Cu in an amount of 0.1 to 5.0% for Co or Ni, and 0.1 to 2.0% for Cu.
 5. The process for producing a martensitic heat-resisting steel according to claim 3, wherein said hot working is rolling for producing a plate product and a tube product.
 6. The process for producing a martensitic heat-resisting steel according to claim 3, wherein said hot working is forging. 